0001315257-26-000048 | 10-Q | XBRL Viewer

8.3

0.6

Common Stock dividends ($0.09, $0.08, $0.18 and $0.16 per share)

2.5

(3.5)

(0.0)

29.8

0.0

4.4

^[1]

^[2]

25.2

Balance at end of period at Jun. 30, 2025

(29.2)

527.1

$ 0.3

326.1

489.3

(61.2)

$ (227.7)

0.3

Balance at beginning of period (in shares) at Dec. 31, 2024

25,761,000

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Balance at end of period (in shares) at Jun. 30, 2025

397,000

26,158,000

Treasury Stock, balance at beginning of period (in shares) at Dec. 31, 2024

(5,480,000)

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Treasury Stock, balance at end of period (in shares) at Jun. 30, 2025

(966,000)

(6,446,000)

Balance at beginning of period at Mar. 31, 2025

498.3

$ 0.3

324.1

474.5

(83.3)

$ (217.6)

0.3

Increase (Decrease) in Stockholders' Equity [Roll Forward]

1.7

0.3

Common Stock dividends ($0.09, $0.08, $0.18 and $0.16 per share)

16.4

(1.6)

(0.0)

20.6

0.0

1.4

^[1]

^[2]

0.1

Balance at end of period at Jun. 30, 2025

(10.1)

$ 527.1

$ 0.3

326.1

489.3

(61.2)

$ (227.7)

0.3

Balance at beginning of period (in shares) at Mar. 31, 2025

26,120,000

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Balance at end of period (in shares) at Jun. 30, 2025

38,000

26,158,000

Treasury Stock, balance at beginning of period (in shares) at Mar. 31, 2025

(6,116,000)

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Treasury Stock, balance at end of period (in shares) at Jun. 30, 2025

(330,000)

(6,446,000)

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Common Stock Outstanding (in shares)

19,712,000

Balance at beginning of period at Dec. 31, 2025

$ 574.3

$ 0.3

332.4

539.4

(61.4)

$ (236.7)

0.3

Increase (Decrease) in Stockholders' Equity [Roll Forward]

6.8

0.5

Common Stock dividends ($0.09, $0.08, $0.18 and $0.16 per share)

(140.4)

(3.7)

(0.3)

(6.5)

(6.2)

(0.3)

0.1

^[1]

^[2]

0.5

Balance at end of period at Jun. 30, 2026

(44.3)

$ 387.0

$ 0.3

339.7

395.0

(67.0)

$ (281.0)

0.0

Balance at beginning of period (in shares) at Dec. 31, 2025

26,213,000

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Balance at end of period (in shares) at Jun. 30, 2026

611,000

26,824,000

Treasury Stock, balance at beginning of period (in shares) at Dec. 31, 2025

(6,757,247)

(6,757,000)

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Treasury Stock, balance at end of period (in shares) at Jun. 30, 2026

(1,164,000)

(7,920,741)

(7,921,000)

Balance at beginning of period at Mar. 31, 2026

$ 549.5

$ 0.3

336.4

544.3

(65.8)

$ (265.7)

0.0

Increase (Decrease) in Stockholders' Equity [Roll Forward]

2.9

0.4

Common Stock dividends ($0.09, $0.08, $0.18 and $0.16 per share)

(147.5)

(1.8)

(0.0)

(0.7)

0.0

(0.7)

^[1]

^[2]

0.2

Balance at end of period at Jun. 30, 2026

(15.3)

$ 387.0

$ 0.3

$ 339.7

$ 395.0

$ (67.0)

$ (281.0)

$ 0.0

Balance at beginning of period (in shares) at Mar. 31, 2026

26,790,000

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Balance at end of period (in shares) at Jun. 30, 2026

34,000

26,824,000

Treasury Stock, balance at beginning of period (in shares) at Mar. 31, 2026

(7,560,000)

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Treasury Stock, balance at end of period (in shares) at Jun. 30, 2026

(361,000)

(7,920,741)

(7,921,000)

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Common Stock Outstanding (in shares)

18,903,000

[1]	Amounts reclassified from accumulated other comprehensive income to net income related to derivative financial instruments, net of tax, were $0.5 million and $0.9 million during the three months ended June 30, 2026 and 2025, respectively, and $0.9 million and $1.5 million during the six months ended June 30, 2026 and 2025, respectively.
[2]	Amounts reclassified from accumulated other comprehensive income to net income consist of amounts shown for pension adjustments. This component of accumulated other comprehensive income is included in the computation of net periodic pension cost as disclosed in Note 10 – Pensions and Post-Retirement Benefit Plans.

Commitments and Contingent Liabilities - Summary of Changes in Accrued Liability for Environmental Matters (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2026	Dec. 31, 2025
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of period	$ 10.2	$ 10.3
Expense	0.2	0.5
Cash expenditures	(0.3)	(0.4)
Revision of reserves	(0.1)	(0.3)
Currency translation	(0.0)	0.1
Balance at end of period	$ 10.0	$ 10.2

Stock-based Compensation - Summary of Stock Options and Performance Award Fair Value Assumptions (Details) - Performance Stock Units	6 Months Ended
	Jun. 30, 2026 $ / shares
January 2026 Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date price per share of performance award (in dollars per share)	$ 26.93
Expected volatility	37.74%
Risk-free interest rate	3.53%
Look-back period in years	3 years
Grant date fair value per share (in dollars per share)	$ 27.97
May 2026 Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date price per share of performance award (in dollars per share)	$ 41.54
Expected volatility	39.03%
Risk-free interest rate	4.06%
Look-back period in years	3 years
Grant date fair value per share (in dollars per share)	$ 68.25

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Earnings and Dividends per Common Share

Earnings and Dividends per Common Share

6 Months Ended

Jun. 30, 2026

Earnings Per Share [Abstract]

The following table sets forth the computation of basic and diluted earnings per common share:


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions, except share and per share amounts)
Net (loss) income	$	(147.5)	$	16.4	$	(140.4)	$	2.5
Weighted average common shares outstanding (in thousands):
Basic	19,128		19,883		19,338		20,123
Effect of dilutive securities	0		352		0		333
Diluted	19,128		20,235		19,338		20,456
(Loss) earnings per common share:
Basic	$	(7.71)	$	0.83	$	(7.26)	$	0.13
Diluted	$	(7.71)	$	0.81	$	(7.26)	$	0.12
Antidilutive securities excluded from computation of diluted earnings per common share	701		714		715		771

On August 5, 2026, we declared a quarterly dividend of $0.09 per common share, payable on September 14, 2026 to shareholders of record as of August 28, 2026.

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2026

Fair Value Disclosures [Abstract]

Schedule of Company's Financial Instruments

The following table presents the estimated fair values and the related carrying amounts of our financial instruments:


	June 30, 2026				December 31, 2025
	Fair Value		Carrying Value		Fair Value		Carrying Value
(Dollars in millions)
Assets - Investments and Other Assets	$	1.4	$	1.4	$	1.3	$	1.3
Liabilities - Debt (including current portion)	$	912.9	$	905.7	$	933.6	$	928.3

Income Taxes (Tables)

6 Months Ended

Jun. 30, 2026

Income Tax Disclosure [Abstract]

Summary of Income Taxes Reconciled with Federal Statutory Rate

The estimated annual effective income tax rate differs from the U.S. federal statutory tax rate due to:


	June 30,
	2026		2025
Federal income tax rate	21.0	%	21.0	%
Foreign earnings taxed at different rates	(2.8)		5.5
Nondeductible expenses	(1.1)		2.2
State income taxes, net of federal tax benefit	1.0		1.9
Change in tax contingency reserves	(0.2)		0.3
U.S. tax on international operations, net of credits	0.0		0.7
Estimated annual effective income tax rate	17.9	%	31.6	%

Derivative Financial Instruments - Summary of Outstanding Copper Swap Contracts (Details) - Copper Swap Contracts - Not designated as hedges £ in Millions, $ in Millions	Jun. 30, 2026 USD ($)	Jun. 30, 2026 GBP (£)	Dec. 31, 2025 USD ($)	Dec. 31, 2025 GBP (£)
Derivatives Fair Value [Line Items]
Units Outstanding (in Pounds) \| £		£ 26.8		£ 25.6
Net Fair Value – Asset \| $	$ 20.2		$ 31.4

Restructuring - Summary of Restructuring Activities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		30 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026
Restructuring Cost and Reserve [Line Items]
Total impairment and restructuring	$ 215.8	$ 17.6	$ 223.6	$ 37.6	$ 292.4
Severance and employee benefits \| Stickney Shutdown
Restructuring Cost and Reserve [Line Items]
Total impairment and restructuring	2.0	0.0	2.0	0.0	2.0
Severance and employee benefits \| Phthalic Anhydride Shutdown
Restructuring Cost and Reserve [Line Items]
Total impairment and restructuring	0.0	0.5	0.1	0.6	1.1
Impairment \| Stickney Shutdown
Restructuring Cost and Reserve [Line Items]
Total impairment and restructuring	164.6	0.0	164.6	0.0	164.6
Depreciation and asset disposal costs \| Stickney Shutdown
Restructuring Cost and Reserve [Line Items]
Total impairment and restructuring	8.5	0.0	8.5	0.0	8.5
Depreciation and asset disposal costs \| Phthalic Anhydride Shutdown
Restructuring Cost and Reserve [Line Items]
Total impairment and restructuring	0.2	4.6	0.2	18.5	26.8
Plant cleaning, waste disposal and demolition costs \| Stickney Shutdown
Restructuring Cost and Reserve [Line Items]
Total impairment and restructuring	36.4	0.0	36.4	0.0	36.4
Plant cleaning, waste disposal and demolition costs \| Phthalic Anhydride Shutdown
Restructuring Cost and Reserve [Line Items]
Total impairment and restructuring	0.9	7.9	1.3	7.9	14.7
Workforce reduction program
Restructuring Cost and Reserve [Line Items]
Total impairment and restructuring	0.0	0.2	0.0	3.3	8.3
Consulting services
Restructuring Cost and Reserve [Line Items]
Total impairment and restructuring	2.7	4.4	5.1	7.3	21.0
Other restructuring costs
Restructuring Cost and Reserve [Line Items]
Total impairment and restructuring	$ 0.5	$ 0.0	$ 5.4	$ 0.0	$ 9.0

Derivative Financial Instruments - Additional Information (Details) gal in Millions, $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2026 USD ($) gal	Dec. 31, 2025 gal	Dec. 31, 2023 USD ($)
Derivative [Line Items]
Maximum period hedged in cash flow hedge	36 months
Unrealized gains (loss), net of tax, expected to be reclassified from other comprehensive income into earnings	$ 1.3
Total derivative contracts \| gal	2.9	3.8
Unrealized gains, reclassification period	12 months
Interest Rate Swap
Derivative [Line Items]
Unrealized gains (loss), net of tax, expected to be reclassified from other comprehensive income into earnings	$ (0.1)
Derivative, notional value			$ 400.0
Fixed interest rate of loan portion			3.97%
Interest Rate Swap One
Derivative [Line Items]
Derivative, notional value	$ 100.0
Fixed interest rate of loan portion	4.10%
Interest Rate Swap Two
Derivative [Line Items]
Derivative, notional value	$ 150.0
Fixed interest rate of loan portion	4.01%
Interest Rate Swap Three
Derivative [Line Items]
Derivative, notional value	$ 150.0
Fixed interest rate of loan portion	3.99%
Commodity Price Hedging
Derivative [Line Items]
Unrealized gains (loss), net of tax, expected to be reclassified from other comprehensive income into earnings	$ 0.7

Restructuring - Additional Information (Details) $ in Millions	1 Months Ended	3 Months Ended
	Feb. 28, 2026 mi	Mar. 31, 2026 USD ($) facility
Restructuring and Related Activities [Abstract]
Number of facilities in idle \| facility		2
Number of miles between facility taking on production from idle facility \| mi	60
Non cash gain on liquidation of business \| $		$ 4.0

Restructuring - Summary of Pre-tax Charges, Restructuring Activities (Details) $ in Millions	Jun. 30, 2026 USD ($)
Minimum \| Stickney Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	$ 233.0
Minimum \| Phthalic Anhydride Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	50.0
Minimum \| Cash Restructuring Costs
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	79.0
Minimum \| Severance and employee benefits \| Stickney Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	5.0
Minimum \| Severance and employee benefits \| Phthalic Anhydride Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	1.0
Minimum \| Plant cleaning, waste disposal and demolition costs \| Stickney Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	52.0
Minimum \| Plant cleaning, waste disposal and demolition costs \| Phthalic Anhydride Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	21.0
Minimum \| Noncash Restructuring Costs
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	204.0
Minimum \| Impairment, Depreciation and Asset Disposal Costs \| Stickney Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	176.0
Minimum \| Depreciation and asset disposal costs \| Phthalic Anhydride Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	28.0
Maximum \| Stickney Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	252.0
Maximum \| Phthalic Anhydride Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	54.0
Maximum \| Cash Restructuring Costs
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	93.0
Maximum \| Severance and employee benefits \| Stickney Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	5.0
Maximum \| Severance and employee benefits \| Phthalic Anhydride Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	1.0
Maximum \| Plant cleaning, waste disposal and demolition costs \| Stickney Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	62.0
Maximum \| Plant cleaning, waste disposal and demolition costs \| Phthalic Anhydride Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	25.0
Maximum \| Noncash Restructuring Costs
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	213.0
Maximum \| Impairment, Depreciation and Asset Disposal Costs \| Stickney Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	185.0
Maximum \| Depreciation and asset disposal costs \| Phthalic Anhydride Shutdown
Restructuring Cost and Reserve [Line Items]
Cumulative restructuring charges, expected	$ 28.0

Basis of Presentation and New Accounting Pronouncements	6 Months Ended
Basis of Presentation and New Accounting Pronouncements	Jun. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and New Accounting Pronouncements	Basis of Presentation and New Accounting Pronouncements Basis of Presentation – The accompanying unaudited condensed consolidated financial statements and related disclosures have been prepared in accordance with accounting principles generally accepted in the United States applicable to interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments considered necessary for a fair presentation of Koppers Holdings Inc.’s and its subsidiaries’ (Koppers, Koppers Holdings, the Company, we or us) financial position and interim results as of and for the periods presented have been included. All such adjustments are of a normal recurring nature unless disclosed otherwise. Because our business is seasonal, results for interim periods are not necessarily indicative of those that may be expected for a full year. The Condensed Consolidated Balance Sheet as of December 31, 2025 has been summarized from the audited balance sheet contained in the Annual Report on Form 10-K as of and for the year ended December 31, 2025. Certain prior period amounts in the condensed consolidated financial statements and notes to the condensed consolidated financial statements have been reclassified to conform to the current period’s presentation. The financial information included herein should be read in conjunction with our audited consolidated financial statements and related notes included in our Annual Report on Form 10-K as of and for the year ended December 31, 2025. New Accounting Pronouncements – In November 2024, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2024-03, Income Statement - Reporting Comprehensive Income (Topic 220): Expense Disaggregation Disclosures. This ASU requires the disaggregation of certain expenses into specific categories, such as purchases of inventory, employee compensation, depreciation and intangible asset amortization. Additionally, the amendments require disclosure of the total amount of selling expenses and an annual disclosure of the definition of selling expenses. ASU No. 2024-03 is effective for fiscal years beginning after December 15, 2026 and for interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. The amendments should be applied either prospectively to financial statements issued for reporting periods after the effective date of this ASU or retrospectively to any and all prior periods presented in the financial statements. We are currently evaluating this ASU to determine its impact on our disclosures.

Pensions and Post-Retirement Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2026

Retirement Benefits [Abstract]

Summary of Components of Net Periodic Benefit Cost for Pension Plans

The following table provides the components of net periodic benefit cost for the pension plans:


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Service cost	$	0.0	$	1.3	$	0.1	$	1.6
Interest cost	0.6		0.7		1.2		1.9
Expected return on plan assets	(0.5)		(0.5)		(1.0)		(1.3)
Amortization of net loss	0.3		0.2		0.5		0.6
Settlement	0.0		0.0		0.0		29.0
Net periodic benefit cost	$	0.4	$	1.7	$	0.8	$	31.8
Defined contribution plan expense	$	1.7	$	1.2	$	4.6	$	4.5

Derivative Financial Instruments - Summary of Fair Value of Outstanding Derivative Contracts Recorded in Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Derivative [Line Items]
Net asset (liability) on balance sheet	$ 21.0	$ 27.8
Accumulated other comprehensive gain, net of tax	2.6	0.1
Balance Sheet Location: us-gaap:AccruedLiabilitiesCurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	(0.9)	(2.6)
Balance Sheet Location: us-gaap:OtherAssetsNoncurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	0.4
Balance Sheet Location: us-gaap:OtherLiabilitiesNoncurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	(1.7)	(1.1)
Balance Sheet Location: kop:DerivativeFairValueOfDerivativeCurrentAssets
Derivative [Line Items]
Net asset (liability) on balance sheet	23.2	31.5
Copper Swap Contracts
Derivative [Line Items]
Net asset (liability) on balance sheet	20.2	31.4
Accumulated other comprehensive gain, net of tax	1.7	2.5
Copper Swap Contracts \| Balance Sheet Location: us-gaap:AccruedLiabilitiesCurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	0.0	0.0
Copper Swap Contracts \| Balance Sheet Location: us-gaap:OtherAssetsNoncurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	0.0
Copper Swap Contracts \| Balance Sheet Location: us-gaap:OtherLiabilitiesNoncurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	(0.6)	0.0
Copper Swap Contracts \| Balance Sheet Location: kop:DerivativeFairValueOfDerivativeCurrentAssets
Derivative [Line Items]
Net asset (liability) on balance sheet	20.8	31.4
Heating Oil Contracts
Derivative [Line Items]
Net asset (liability) on balance sheet	2.1	(0.4)
Accumulated other comprehensive gain, net of tax	0.0	0.0
Heating Oil Contracts \| Balance Sheet Location: us-gaap:AccruedLiabilitiesCurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	0.0	(0.4)
Heating Oil Contracts \| Balance Sheet Location: us-gaap:OtherAssetsNoncurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	0.4
Heating Oil Contracts \| Balance Sheet Location: us-gaap:OtherLiabilitiesNoncurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	0.0	0.0
Heating Oil Contracts \| Balance Sheet Location: kop:DerivativeFairValueOfDerivativeCurrentAssets
Derivative [Line Items]
Net asset (liability) on balance sheet	1.7	0.0
Foreign Currency Forward Contracts
Derivative [Line Items]
Net asset (liability) on balance sheet	(0.1)	0.0
Accumulated other comprehensive gain, net of tax	0.0	0.0
Foreign Currency Forward Contracts \| Balance Sheet Location: us-gaap:AccruedLiabilitiesCurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	(0.1)	0.0
Foreign Currency Forward Contracts \| Balance Sheet Location: us-gaap:OtherAssetsNoncurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	0.0
Foreign Currency Forward Contracts \| Balance Sheet Location: us-gaap:OtherLiabilitiesNoncurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	0.0	0.0
Foreign Currency Forward Contracts \| Balance Sheet Location: kop:DerivativeFairValueOfDerivativeCurrentAssets
Derivative [Line Items]
Net asset (liability) on balance sheet	0.0	0.0
Interest Rate Swap Contracts
Derivative [Line Items]
Net asset (liability) on balance sheet	(1.2)	(3.2)
Accumulated other comprehensive gain, net of tax	0.9	(2.4)
Interest Rate Swap Contracts \| Balance Sheet Location: us-gaap:AccruedLiabilitiesCurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	(0.8)	(2.2)
Interest Rate Swap Contracts \| Balance Sheet Location: us-gaap:OtherAssetsNoncurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	0.0
Interest Rate Swap Contracts \| Balance Sheet Location: us-gaap:OtherLiabilitiesNoncurrent
Derivative [Line Items]
Net asset (liability) on balance sheet	(1.1)	(1.1)
Interest Rate Swap Contracts \| Balance Sheet Location: kop:DerivativeFairValueOfDerivativeCurrentAssets
Derivative [Line Items]
Net asset (liability) on balance sheet	$ 0.7	$ 0.1

Earnings and Dividends per Common Share - Additional Information (Details) - $ / shares		3 Months Ended		6 Months Ended
	Aug. 05, 2026	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Quarterly dividend declared per common share (in dollars per share)		$ 0.09	$ 0.08	$ 0.18	$ 0.16
Subsequent Event
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Quarterly dividend declared per common share (in dollars per share)	$ 0.09

Segment Information (Tables)

6 Months Ended

Jun. 30, 2026

Segment Reporting [Abstract]

Summary of Segment Revenues for Significant Product Lines

Segment Revenues for Significant Product Lines


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Railroad and Utility Products and Services:
Railroad treated products	$	147.3	$	150.9	$	281.5	$	297.2
Utility poles	86.7		75.8		161.5		143.7
Railroad infrastructure products and services	11.9		23.7		22.9		44.5
Total Railroad and Utility Products and Services	$	245.9	$	250.4	$	465.9	$	485.4
Performance Chemicals:
Wood preservative products and other	$	168.2	$	150.8	$	310.3	$	271.7
Carbon Materials and Chemicals:
Pitch and related products	$	75.0	$	74.4	$	145.2	$	139.6
Carbon black feedstock and distillates	22.9		14.4		36.7		28.6
Naphthalene, phthalic anhydride, and other chemicals	8.1		14.8		17.3		36.0
Total Carbon Materials and Chemicals	$	106.0	$	103.6	$	199.2	$	204.2
Total	$	520.1	$	504.8	$	975.4	$	961.3

Summary of Results of Segment Operations

Segment Expenses


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Cost of sales:
Railroad and Utility Products and Services	$	204.2	$	201.8	$	380.2	$	392.5
Performance Chemicals	119.3		108.6		229.5		187.6
Carbon Materials and Chemicals	87.6		80.2		170.1		161.2
Total	$	411.1	$	390.6	$	779.8	$	741.3
Selling, general and administrative expenses:
Railroad and Utility Products and Services	$	17.2	$	17.1	$	35.5	$	35.3
Performance Chemicals	14.7		15.4		29.6		30.5
Carbon Materials and Chemicals	9.0		7.0		17.5		14.8
Total	$	40.9	$	39.5	$	82.6	$	80.6
Other (income) expense to reconcile to Adjusted EBITDA(1):
Railroad and Utility Products and Services	$	(1.2)	$	(0.1)	$	1.9	$	0.5
Performance Chemicals	(3.5)		(1.9)		(12.3)		4.8
Carbon Materials and Chemicals	1.8		(0.4)		3.1		1.5
Total	$	(2.9)	$	(2.4)	$	(7.3)	$	6.8
Adjusted EBITDA:
Railroad and Utility Products and Services	$	25.7	$	31.6	$	48.3	$	57.1
Performance Chemicals	37.7		28.7		63.5		48.8
Carbon Materials and Chemicals	7.6		16.8		8.5		26.7
Total	$	71.0	$	77.1	$	120.3	$	132.6

(1)Other (income) expense amounts primarily relate to miscellaneous (income) expense and the adjustments to reconcile to adjusted EBITDA such as acquisition-related charges, LIFO inventory effects and mark-to-market commodity hedging.

Segment Adjusted EBITDA


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Adjusted EBITDA:
Railroad and Utility Products and Services	$	25.7	$	31.6	$	48.3	$	57.1
Performance Chemicals	37.7		28.7		63.5		48.8
Carbon Materials and Chemicals	7.6		16.8		8.5		26.7
Items excluded from the determination of segment profit:
Acquisition inventory step-up amortization	(0.5)		0.0		(0.8)		0.0
Amortization of cloud-based software implementation costs	(0.7)		(0.5)		(1.2)		(0.8)
(Loss) gain on sale of assets	(0.4)		0.0		3.9		0.3
Impairment, restructuring and plant closure costs(1)	(215.8)		(17.6)		(223.6)		(37.6)
LIFO benefit(2)	2.3		0.7		3.5		2.5
Mark-to-market commodity hedging (losses) gains	(3.0)		0.7		(6.9)		9.8
Pension settlement and expense	0.0		(1.2)		0.0		(30.2)
Depreciation and amortization	(17.9)		(18.0)		(37.3)		(36.0)
Interest expense	(15.0)		(17.3)		(30.0)		(33.9)
Income tax benefit (provision)	32.5		(7.5)		31.7		(4.2)
Net (loss) income	$	(147.5)	$	16.4	$	(140.4)	$	2.5

(1)See Note 2 - Restructuring.

(2)The LIFO expense adjustment removes the entire impact of LIFO and effectively reflects the results as if we were on a first-in, first-out (FIFO) inventory basis.

Other Segment Disclosures


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Intersegment revenues:
Performance Chemicals	$	8.5	$	7.9	$	15.7	$	14.8
Carbon Materials and Chemicals	28.1		23.2		51.2		45.4
Total	$	36.6	$	31.1	$	66.9	$	60.2
Depreciation and amortization expense:
Railroad and Utility Products and Services	$	8.2	$	8.5	$	16.4	$	17.0
Performance Chemicals	4.0		4.1		8.3		7.9
Carbon Materials and Chemicals	5.7		5.4		12.6		11.1
Total	$	17.9	$	18.0	$	37.3	$	36.0
Capital expenditures:
Railroad and Utility Products and Services	$	5.1	$	4.2	$	10.5	$	9.3
Performance Chemicals	4.0		2.4		6.8		5.9
Carbon Materials and Chemicals	2.9		5.2		5.9		10.2
Corporate	0.3		0.3		0.5		1.0
Total	$	12.3	$	12.1	$	23.7	$	26.4

Summary of Tangible and Intangible Assets by Segments

Segment Assets


	June 30, 2026		December 31, 2025
(Dollars in millions)
Segment assets:
Railroad and Utility Products and Services	$	833.5	$	827.5
Performance Chemicals	557.5		536.6
Carbon Materials and Chemicals(1)	305.1		486.7
Corporate	26.2		36.0
Total	$	1,722.3	$	1,886.8
Goodwill:
Railroad and Utility Products and Services	$	156.5	$	156.4
Performance Chemicals	172.6		173.0
Total	$	329.1	$	329.4

(1)See Note 2 - Restructuring.

Commitments and Contingent Liabilities - Additional Information (Details) $ in Millions	1 Months Ended	6 Months Ended
	Jan. 31, 2017 USD ($)	Jun. 30, 2026 USD ($) site party claim plaintiff plant	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Nov. 30, 2024 party
Loss Contingencies [Line Items]
Environmental remediation and regulation liability		$ 10.0	$ 10.2	$ 10.3
Accrued liability for environmental matters, current		$ 1.6	$ 1.8
Environmental Loss Contingency, Current, Statement of Financial Position [Extensible Enumeration]		Liabilities, Current	Liabilities, Current
Portland Harbor and Newark Bay CERCLA sites
Loss Contingencies [Line Items]
Costs of participating in PRP group		$ 3.8
Portland Harbor
Loss Contingencies [Line Items]
Number of claims \| claim		2
Portland Harbor, Trustee Claims
Loss Contingencies [Line Items]
Number of claims settled \| claim		1
Number of plaintiffs filing an appeal \| plaintiff		1
Oregon
Loss Contingencies [Line Items]
Number of potential responsible parties \| party		80			60
Net present value of selected remedy estimation	$ 1,100.0
Undiscounted cost of selected remedy estimation	$ 1,700.0
United States
Loss Contingencies [Line Items]
Environmental remediation and regulation liability		$ 3.6
United States \| Performance Chemicals
Loss Contingencies [Line Items]
Number of plant sites \| plant		2
United States \| Utility and Industrial Products
Loss Contingencies [Line Items]
Number of plant sites \| plant		1
Australia \| Performance Chemicals
Loss Contingencies [Line Items]
Number of plant sites \| plant		1
Environmental remediation and regulation liability		$ 1.2
Beazer East
Loss Contingencies [Line Items]
Sites listed on National Priorities List \| site		1

Restructuring (Tables)

6 Months Ended

Jun. 30, 2026

Restructuring and Related Activities [Abstract]

Summary of Restructuring Activities

The following table summarizes restructuring activities:


	Three Months Ended June 30,				Six Months Ended June 30,				Cumulative Total
	2026		2025		2026		2025
(Dollars in millions)
Stickney Shutdown:
Severance, retention and employee benefits	$	2.0	$	0.0	$	2.0	$	0.0	$	2.0
Impairment	164.6		0.0		164.6		0.0		164.6
Depreciation and asset disposal costs	8.5		0.0		8.5		0.0		8.5
Plant cleaning, waste disposal and demolition costs	36.4		0.0		36.4		0.0		36.4
Phthalic Anhydride Shutdown:
Severance and employee benefits	0.0		0.5		0.1		0.6		1.1
Depreciation and asset disposal costs	0.2		4.6		0.2		18.5		26.8
Plant cleaning, waste disposal and demolition costs	0.9		7.9		1.3		7.9		14.7
Workforce reduction program	0.0		0.2		0.0		3.3		8.3
Consulting services	2.7		4.4		5.1		7.3		21.0
Other restructuring costs	0.5		0.0		5.4		0.0		9.0
Total impairment and restructuring	$	215.8	$	17.6	$	223.6	$	37.6	$	292.4

We expect these combined actions to result in the following cumulative charges, which includes the amounts already spent in the above table:


Expected Totals	Low		High
(Dollars in millions)
Severance, retention and employee benefits (cash)	$	5.0	$	5.0
Impairment, depreciation and asset disposal costs (non-cash)	176.0		185.0
Plant cleaning, waste disposal and demolition costs (cash)	52.0		62.0
Stickney Shutdown Total Pre-tax Charges	$	233.0	$	252.0

Severance, retention and employee benefits (cash)	$	1.0	$	1.0
Depreciation and asset disposal costs (non-cash)	28.0		28.0
Plant cleaning, waste disposal and demolition costs (cash)	21.0		25.0
Phthalic Anhydride Shutdown Total Pre-tax Charges	$	50.0	$	54.0

Total Cash Charges	$	79.0	$	93.0
Total Non-Cash Charges	$	204.0	$	213.0

Summary of Details of Plant Closures and Restructuring Liabilities

The following table includes details of our Stickney shutdown, phthalic anhydride shutdown and workforce reduction program liabilities:


	Stickney Shutdown		Phthalic Anhydride Shutdown		Workforce Reduction Program
(Dollars in millions)
Liability at December 31, 2024	$	0.0	$	0.0	$	4.4
Accrual	0.0		13.5		1.2
Cash paid	0.0		(8.1)		(5.0)
Liability at December 31, 2025	$	0.0	$	5.4	$	0.6
Accrual(1)	38.4		1.3		0.0
Cash paid	0.0		(2.3)		(0.6)
Liability at June 30, 2026	$	38.4	$	4.4	$	0.0

(1)Approximately $18.5 million of the Stickney shutdown accrual is a short-term asset retirement obligation, which is included in accrued liabilities in the condensed consolidated balance sheet.

Fair Value Measurements (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Fair Value
Financial assets:
Assets - Investments and Other Assets	$ 1.4	$ 1.3
Financial liabilities:
Liabilities - Debt (including current portion)	912.9	933.6
Carrying Value
Financial assets:
Assets - Investments and Other Assets	1.4	1.3
Financial liabilities:
Liabilities - Debt (including current portion)	$ 905.7	$ 928.3

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
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-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
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-Name Accounting Standards Codification
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-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

Reference 10: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
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Reference 11: http://www.xbrl.org/2003/role/exampleRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Stock-based Compensation - Summary of Status and Activity of Stock Options (Details) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2026 USD ($) $ / shares shares
Options
Outstanding, beginning balance (in shares) \| shares	507,130
Exercised (in shares) \| shares	(77,409)
Expired (in shares) \| shares	(6,664)
Outstanding, ending balance (in shares) \| shares	423,057
Exercisable (in shares) \| shares	423,057
Weighted Average Exercise Price per Option
Beginning balance (in dollars per share) \| $ / shares	$ 28.62
Exercised (in dollars per share) \| $ / shares	20.25
Expired (in dollars per share) \| $ / shares	32.19
Ending balance (in dollars per share) \| $ / shares	30.10
Exercisable (in dollars per share) \| $ / shares	$ 30.10
Stock Options Additional Disclosures
Weighted Average Remaining Contractual Term, Outstanding	3 years 4 months 13 days
Weighted Average Remaining Contractual Term, Exercisable	3 years 4 months 13 days
Aggregate Intrinsic Value, Outstanding \| $	$ 6.3
Aggregate Intrinsic Value, Exercisable \| $	$ 6.3

Income Taxes

6 Months Ended

Jun. 30, 2026

Income Tax Disclosure [Abstract]

Income Taxes

Effective Tax Rate – The income tax provision for interim periods is comprised of an estimated annual effective income tax rate applied to current year ordinary income and tax associated with discrete items. These discrete items generally relate to excess stock compensation deductions, changes in tax laws, adjustments to unrecognized tax benefits and changes of estimated tax liability to the actual liability determined upon filing income tax returns. To determine the annual effective tax rate, management is required to make estimates of annual pre-tax income in each domestic and foreign jurisdiction in which we conduct business. Entities that have historical pre-tax losses and current year estimated pre-tax losses that are not projected to generate a future benefit are excluded from the estimated annual effective income tax rate.

The estimated annual effective income tax rate differs from the U.S. federal statutory tax rate due to:


	June 30,
	2026		2025
Federal income tax rate	21.0	%	21.0	%
Foreign earnings taxed at different rates	(2.8)		5.5
Nondeductible expenses	(1.1)		2.2
State income taxes, net of federal tax benefit	1.0		1.9
Change in tax contingency reserves	(0.2)		0.3
U.S. tax on international operations, net of credits	0.0		0.7
Estimated annual effective income tax rate	17.9	%	31.6	%

The estimated annual effective income tax rate for 2026 is materially lower than the estimated annual effective income tax rate for 2025 due to the Stickney shutdown tax benefit being recorded at a tax rate of approximately 23 percent, which is materially less than the tax rate that is recorded on the pre-tax income from our worldwide operations. The estimated annual effective tax rate for 2026 is less than the federal income tax rate since the estimated result of our worldwide operations is a pre-tax loss. The effect of the higher foreign tax rate and the other reconciling tax expense items in the above table reduce the estimated annual effective income tax rate when there is a pre-tax loss.

Income taxes as a percentage of pre-tax income were 18.1 percent and 18.4 percent for the three and six months ended June 30, 2026, respectively, and 31.4 percent and 62.7 percent for the three and six months ended June 30, 2025, respectively.

The effective income tax rate for the three and six months ended June 30, 2026 was slightly higher than the respective estimated annual effective income tax rate due to various discrete items, which were not material in the aggregate or individually.

The effective income tax rate for the three months ended June 30, 2025 was slightly lower than the respective estimated annual effective income tax rate due to various discrete items, which were not material in the aggregate or individually. The effective income tax rate for the six months ended June 30, 2025 was significantly higher than the respective estimated annual effective income tax rate due to the loss on pension settlement, which was treated as a discrete item.

During the year, management regularly updates estimates of pre-tax income and income tax expense based on changes in pre-tax income projections by taxable jurisdiction, repatriation of foreign earnings, unrecognized tax benefits and other tax matters. To the extent that actual results vary from these estimates, the actual annual effective income tax rate at the end of the year could be materially different from the estimated annual effective income tax rate as of the six months ended June 30, 2026.

Effective January 1, 2024, certain jurisdictions in which we operate have enacted legislation that is consistent with one or more Organization for Economic Co-operation and Development Global Anti-Base Erosion Model Rules (commonly referred to as "Pillar Two"). These Pillar Two rules include minimum domestic top up taxes, income inclusion rules and undertaxed profit rules all aimed to ensure that multinational business corporations pay a minimum effective corporate tax rate of 15 percent in each jurisdiction in which they operate. We have analyzed our tax profile by jurisdiction and do not expect to incur top up taxes in 2026.

Unrecognized Tax Benefits – We file income tax returns in the U.S. federal jurisdiction, individual U.S. state jurisdictions and non-U.S. jurisdictions. With few exceptions, we are no longer subject to U.S. federal, U.S. state, or non-U.S. income tax examinations by tax authorities for years prior to 2020.

As of June 30, 2026 and December 31, 2025, unrecognized tax benefits of $1.2 million and $1.1 million, respectively, would affect the effective tax rate if recognized. We do not anticipate material changes to the amount of unrecognized tax benefits within the next twelve months.

The entire disclosure for income tax.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/exampleRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Derivative Financial Instruments - Summary of Net Currency Units Outstanding (Details) £ in Millions, $ in Millions, $ in Millions	Jun. 30, 2026 USD ($)	Jun. 30, 2026 GBP (£)	Jun. 30, 2026 AUD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2025 GBP (£)	Dec. 31, 2025 AUD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net currency units outstanding	$ 6.0	£ 0.0	$ 3.2	$ 9.2	£ 0.3	$ 0.0

Pensions and Post-Retirement Benefit Plans - Summary of Components of Net Periodic Benefit Cost for Pension Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Retirement Benefits [Abstract]
Service cost	$ 0.0	$ 1.3	$ 0.1	$ 1.6
Interest cost	0.6	0.7	1.2	1.9
Expected return on plan assets	(0.5)	(0.5)	(1.0)	(1.3)
Amortization of net loss	0.3	0.2	0.5	0.6
Settlement	(0.0)	(0.0)	(0.0)	29.0
Net periodic benefit cost	0.4	1.7	0.8	31.8
Defined contribution plan expense	$ 1.7	$ 1.2	$ 4.6	$ 4.5

Segment Information - Summary of Results of Segment Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Revenues from external customers:
Cost of sales	$ 411.1	$ 390.6	$ 779.8	$ 741.3
Selling, general and administrative expenses:	40.9	39.5	82.6	80.6
Other (income) expense to reconcile to Adjusted EBITDA	(2.9)	(2.4)	(7.3)	6.8
Adjusted EBITDA:
Adjusted EBITDA:	71.0	77.1	120.3	132.6
Items excluded from the determination of segment profit:
Acquisition inventory step-up amortization	(0.5)	(0.0)	(0.8)	(0.0)
Amortization of cloud-based software implementation costs	(0.7)	(0.5)	(1.2)	(0.8)
(Loss) gain on sale of assets	(0.4)	0.0	3.9	0.3
Impairment, restructuring and plant closure costs	(215.8)	(17.6)	(223.6)	(37.6)
LIFO benefit	2.3	0.7	3.5	2.5
Mark-to-market commodity hedging (losses) gains	(3.0)	0.7	(6.9)	9.8
Pension settlement and expense	(0.0)	(1.2)	(0.0)	(30.2)
Depreciation and amortization	(17.9)	(18.0)	(37.3)	(36.0)
Interest expense	(15.0)	(17.3)	(30.0)	(33.9)
Income tax benefit (provision)	32.5	(7.5)	31.7	(4.2)
Net (loss) income	(147.5)	16.4	(140.4)	2.5
Intersegment revenues:	(520.1)	(504.8)	(975.4)	(961.3)
Depreciation and amortization expense:	17.9	18.0	37.3	36.0
Capital expenditures:	12.3	12.1	23.7	26.4
Operating Segments
Items excluded from the determination of segment profit:
Intersegment revenues:	(520.1)	(504.8)	(975.4)	(961.3)
Intersegment revenues:
Items excluded from the determination of segment profit:
Intersegment revenues:	36.6	31.1	66.9	60.2
Corporate
Items excluded from the determination of segment profit:
Capital expenditures:	0.3	0.3	0.5	1.0
Railroad and Utility Products and Services
Revenues from external customers:
Cost of sales	204.2	201.8	380.2	392.5
Selling, general and administrative expenses:	17.2	17.1	35.5	35.3
Other (income) expense to reconcile to Adjusted EBITDA	(1.2)	(0.1)	1.9	0.5
Adjusted EBITDA:
Adjusted EBITDA:	25.7	31.6	48.3	57.1
Items excluded from the determination of segment profit:
Depreciation and amortization expense:	8.2	8.5	16.4	17.0
Railroad and Utility Products and Services \| Operating Segments
Adjusted EBITDA:
Adjusted EBITDA:	25.7	31.6	48.3	57.1
Items excluded from the determination of segment profit:
Intersegment revenues:	(245.9)	(250.4)	(465.9)	(485.4)
Capital expenditures:	5.1	4.2	10.5	9.3
Performance Chemicals
Revenues from external customers:
Cost of sales	119.3	108.6	229.5	187.6
Selling, general and administrative expenses:	14.7	15.4	29.6	30.5
Other (income) expense to reconcile to Adjusted EBITDA	(3.5)	(1.9)	(12.3)	4.8
Adjusted EBITDA:
Adjusted EBITDA:	37.7	28.7	63.5	48.8
Items excluded from the determination of segment profit:
Depreciation and amortization expense:	4.0	4.1	8.3	7.9
Performance Chemicals \| Operating Segments
Adjusted EBITDA:
Adjusted EBITDA:	37.7	28.7	63.5	48.8
Items excluded from the determination of segment profit:
Capital expenditures:	4.0	2.4	6.8	5.9
Performance Chemicals \| Intersegment revenues:
Items excluded from the determination of segment profit:
Intersegment revenues:	8.5	7.9	15.7	14.8
Carbon Materials and Chemicals
Revenues from external customers:
Cost of sales	87.6	80.2	170.1	161.2
Selling, general and administrative expenses:	9.0	7.0	17.5	14.8
Other (income) expense to reconcile to Adjusted EBITDA	1.8	(0.4)	3.1	1.5
Adjusted EBITDA:
Adjusted EBITDA:	7.6	16.8	8.5	26.7
Items excluded from the determination of segment profit:
Depreciation and amortization expense:	5.7	5.4	12.6	11.1
Carbon Materials and Chemicals \| Operating Segments
Adjusted EBITDA:
Adjusted EBITDA:	7.6	16.8	8.5	26.7
Items excluded from the determination of segment profit:
Intersegment revenues:	(106.0)	(103.6)	(199.2)	(204.2)
Capital expenditures:	2.9	5.2	5.9	10.2
Carbon Materials and Chemicals \| Intersegment revenues:
Items excluded from the determination of segment profit:
Intersegment revenues:	$ 28.1	$ 23.2	$ 51.2	$ 45.4

Inventories (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Inventory Disclosure [Abstract]
Raw materials	$ 320.1	$ 351.6
Work in process	13.3	17.3
Finished goods	153.5	147.0
Total	486.9	515.9
Less revaluation to LIFO	101.2	104.7
Inventories, net	$ 385.7	$ 411.2

Segment Information - Additional Information (Details) $ in Millions	6 Months Ended
	Jun. 30, 2026 USD ($) segment	Dec. 31, 2025 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment	3
Contract assets \| $	$ 1.8	$ 1.8

Segment Information

6 Months Ended

Jun. 30, 2026

Segment Reporting [Abstract]

Segment Information

We have three reportable segments: Railroad and Utility Products and Services (RUPS), Performance Chemicals (PC) and Carbon Materials and Chemicals (CMC). Our reportable segments contain multiple aggregated business units since management believes the long-term financial performance of these business units is affected by similar economic conditions. The reportable segments are each managed separately because they manufacture and distribute distinct products with different production processes.

Our RUPS segment primarily sells pressure-treated railroad ties to the railroad industry and treated utility poles to utility markets. Railroad products and services include procuring and treating items such as crossties, switch ties and various types of lumber used for railroad bridges and crossings. Utility products include the pressure treatment of transmission and distribution poles for electric, telephone and broadband utilities. In addition, we provide untreated wood products and rail joint bars, which are steel bars used to join rails together for railroads, to the railroad markets. We also operate a business related to the recovery of used crossties, serving the same customer base as our North American railroad business.

Our PC segment develops, manufactures, and markets wood preservation chemicals and wood treatment technologies and services to a diverse range of end-markets including residential, industrial, commercial construction and agricultural applications.

Our CMC segment is primarily a manufacturer of creosote, carbon pitch, naphthalene and carbon black feedstock. Creosote is used in the treatment of wood and carbon black feedstock is used in the production of carbon black. Carbon pitch is a critical raw material used in the production of aluminum and steel. Naphthalene is used as a surfactant in the production of concrete. See Note 2 - Restructuring for further discussion of the discontinuation of distillation and chemical manufacturing operations in Stickney, Illinois.

Our measure of segment profitability is adjusted income before interest expense, income taxes, depreciation, amortization and certain non-cash and/or non-recurring items that do not contribute directly to management’s evaluation of our operating results (as defined by us, adjusted EBITDA). These non-cash and/or non-recurring items typically include last-in, first-out (LIFO) inventory effects, impairment, restructuring and plant closure costs, significant gains or losses on sale of assets, mark-to-market commodity hedging, acquisition-related charges, amortization of cloud-based software implementation costs and other unusual items. This presentation is consistent with how our chief operating decision maker evaluates the results of operations and makes strategic decisions about the business. In addition, adjusted EBITDA is the primary measure used to determine the level of achievement of management’s short-term incentive goals and related payout, as well as one of the measures used to determine performance and related payouts for certain performance share units granted to management prior to 2026. For these reasons, we believe that adjusted EBITDA represents the most relevant measure of segment profit and loss.

Adjusted EBITDA is reconciled to net income on a consolidated basis, the most directly comparable financial measure determined and reported in accordance with U.S. generally accepted accounting principles (U.S. GAAP). The accounting policies of the reportable segments are the same as those described in the summary of significant accounting policies. Intersegment transactions are eliminated in consolidation.

Contract Balances – The timing of revenue recognition results in both billed accounts receivable and unbilled receivables, both classified as accounts receivable, net of allowance within the condensed consolidated balance sheet. Contract assets of $1.8 million for both periods are recorded within accounts receivable, net of allowance within the condensed consolidated balance sheet as of June 30, 2026 and December 31, 2025.

Segment Revenues for Significant Product Lines


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Railroad and Utility Products and Services:
Railroad treated products	$	147.3	$	150.9	$	281.5	$	297.2
Utility poles	86.7		75.8		161.5		143.7
Railroad infrastructure products and services	11.9		23.7		22.9		44.5
Total Railroad and Utility Products and Services	$	245.9	$	250.4	$	465.9	$	485.4
Performance Chemicals:
Wood preservative products and other	$	168.2	$	150.8	$	310.3	$	271.7
Carbon Materials and Chemicals:
Pitch and related products	$	75.0	$	74.4	$	145.2	$	139.6
Carbon black feedstock and distillates	22.9		14.4		36.7		28.6
Naphthalene, phthalic anhydride, and other chemicals	8.1		14.8		17.3		36.0
Total Carbon Materials and Chemicals	$	106.0	$	103.6	$	199.2	$	204.2
Total	$	520.1	$	504.8	$	975.4	$	961.3

Segment Expenses


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Cost of sales:
Railroad and Utility Products and Services	$	204.2	$	201.8	$	380.2	$	392.5
Performance Chemicals	119.3		108.6		229.5		187.6
Carbon Materials and Chemicals	87.6		80.2		170.1		161.2
Total	$	411.1	$	390.6	$	779.8	$	741.3
Selling, general and administrative expenses:
Railroad and Utility Products and Services	$	17.2	$	17.1	$	35.5	$	35.3
Performance Chemicals	14.7		15.4		29.6		30.5
Carbon Materials and Chemicals	9.0		7.0		17.5		14.8
Total	$	40.9	$	39.5	$	82.6	$	80.6
Other (income) expense to reconcile to Adjusted EBITDA(1):
Railroad and Utility Products and Services	$	(1.2)	$	(0.1)	$	1.9	$	0.5
Performance Chemicals	(3.5)		(1.9)		(12.3)		4.8
Carbon Materials and Chemicals	1.8		(0.4)		3.1		1.5
Total	$	(2.9)	$	(2.4)	$	(7.3)	$	6.8
Adjusted EBITDA:
Railroad and Utility Products and Services	$	25.7	$	31.6	$	48.3	$	57.1
Performance Chemicals	37.7		28.7		63.5		48.8
Carbon Materials and Chemicals	7.6		16.8		8.5		26.7
Total	$	71.0	$	77.1	$	120.3	$	132.6

Segment Adjusted EBITDA


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Adjusted EBITDA:
Railroad and Utility Products and Services	$	25.7	$	31.6	$	48.3	$	57.1
Performance Chemicals	37.7		28.7		63.5		48.8
Carbon Materials and Chemicals	7.6		16.8		8.5		26.7
Items excluded from the determination of segment profit:
Acquisition inventory step-up amortization	(0.5)		0.0		(0.8)		0.0
Amortization of cloud-based software implementation costs	(0.7)		(0.5)		(1.2)		(0.8)
(Loss) gain on sale of assets	(0.4)		0.0		3.9		0.3
Impairment, restructuring and plant closure costs(1)	(215.8)		(17.6)		(223.6)		(37.6)
LIFO benefit(2)	2.3		0.7		3.5		2.5
Mark-to-market commodity hedging (losses) gains	(3.0)		0.7		(6.9)		9.8
Pension settlement and expense	0.0		(1.2)		0.0		(30.2)
Depreciation and amortization	(17.9)		(18.0)		(37.3)		(36.0)
Interest expense	(15.0)		(17.3)		(30.0)		(33.9)
Income tax benefit (provision)	32.5		(7.5)		31.7		(4.2)
Net (loss) income	$	(147.5)	$	16.4	$	(140.4)	$	2.5

(1)See Note 2 - Restructuring.

(2)The LIFO expense adjustment removes the entire impact of LIFO and effectively reflects the results as if we were on a first-in, first-out (FIFO) inventory basis.

Other Segment Disclosures


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Intersegment revenues:
Performance Chemicals	$	8.5	$	7.9	$	15.7	$	14.8
Carbon Materials and Chemicals	28.1		23.2		51.2		45.4
Total	$	36.6	$	31.1	$	66.9	$	60.2
Depreciation and amortization expense:
Railroad and Utility Products and Services	$	8.2	$	8.5	$	16.4	$	17.0
Performance Chemicals	4.0		4.1		8.3		7.9
Carbon Materials and Chemicals	5.7		5.4		12.6		11.1
Total	$	17.9	$	18.0	$	37.3	$	36.0
Capital expenditures:
Railroad and Utility Products and Services	$	5.1	$	4.2	$	10.5	$	9.3
Performance Chemicals	4.0		2.4		6.8		5.9
Carbon Materials and Chemicals	2.9		5.2		5.9		10.2
Corporate	0.3		0.3		0.5		1.0
Total	$	12.3	$	12.1	$	23.7	$	26.4

Segment Assets


	June 30, 2026		December 31, 2025
(Dollars in millions)
Segment assets:
Railroad and Utility Products and Services	$	833.5	$	827.5
Performance Chemicals	557.5		536.6
Carbon Materials and Chemicals(1)	305.1		486.7
Corporate	26.2		36.0
Total	$	1,722.3	$	1,886.8
Goodwill:
Railroad and Utility Products and Services	$	156.5	$	156.4
Performance Chemicals	172.6		173.0
Total	$	329.1	$	329.4

(1)See Note 2 - Restructuring.

The entire disclosure for segment reporting.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-40

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
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-Section 50
-Paragraph 32
-Subparagraph (f)
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Pensions and Post-Retirement Benefit Plans

COVER - shares	6 Months Ended
COVER - shares	Jun. 30, 2026	Jul. 31, 2026
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2026
Document Transition Report	false
Entity File Number	1-32737
Entity Registrant Name	KOPPERS HOLDINGS INC.
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	20-1878963
Entity Address, Address Line One	436 Seventh Avenue
Entity Address, City or Town	Pittsburgh
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15219
City Area Code	412
Local Phone Number	227-2001
Title of 12(b) Security	Common Stock
Trading Symbol	KOP
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		18,911,568
Entity Central Index Key	0001315257
Document Fiscal Year Focus	2026
Document Fiscal Period Focus	Q2
Amendment Flag	false
Current Fiscal Year End Date	--12-31

Stock-based Compensation - Summary of Status and Activity of Non-Vested Stock Units (Details)	6 Months Ended
	Jun. 30, 2026 $ / shares shares
Total Stock Units
Non-vested, beginning balance (in shares)	1,264,468
Granted (in shares)	529,260
Credited from dividends (in shares)	1,022
Performance share adjustment (in shares)	28,505
Vested (in shares)	(580,844)
Forfeited (in shares)	(42,069)
Non-vested, ending balance (in shares)	1,200,342
Weighted Average Grant Date Fair Value per Unit
Beginning balance (in dollars per share) \| $ / shares	$ 35.22
Granted (in dollars per share) \| $ / shares	28.77
Credited from dividends (in dollars per share) \| $ / shares	28.28
Performance share adjustment (in dollars per share) \| $ / shares	28.93
Vested (in dollars per share) \| $ / shares	33.24
Forfeited (in dollars per share) \| $ / shares	36.14
Ending balance (in dollars per share) \| $ / shares	$ 33.17
Restricted Stock Units
Total Stock Units
Non-vested, beginning balance (in shares)	530,237
Granted (in shares)	256,608
Credited from dividends (in shares)	379
Performance share adjustment (in shares)	0
Vested (in shares)	(250,920)
Forfeited (in shares)	(24,882)
Non-vested, ending balance (in shares)	511,422
Performance Stock Units
Total Stock Units
Non-vested, beginning balance (in shares)	734,231
Granted (in shares)	272,652
Credited from dividends (in shares)	643
Performance share adjustment (in shares)	28,505
Vested (in shares)	(329,924)
Forfeited (in shares)	(17,187)
Non-vested, ending balance (in shares)	688,920

Pensions and Post-Retirement Benefit Plans

6 Months Ended

Jun. 30, 2026

Retirement Benefits [Abstract]

We maintain defined benefit and defined contribution plans to provide retirement benefits for employees in the United States, as well as employees outside the United States.

During 2024, we initiated a plan to terminate our largest United States qualified pension plan. In 2025, we completed the irrevocable transfer of $84.5 million of pension liabilities and an equal amount of pension assets to an insurance company. In order to achieve this transfer, additional cash funding of approximately $12 million was required in 2025. In the first quarter of 2025, we recorded a settlement loss of approximately $29.0 million, before tax.

In connection with the planned termination of our defined benefit pension plan in the United Kingdom, in 2021, we entered into a buy-in bulk annuity insurance policy in exchange for a premium payment of $67.8 million, which is subject to adjustment as a result of subsequent data cleansing activities. Under the terms of this buy-in insurance policy, the insurer is liable to pay the benefits of the plan, but the plan still retains full legal responsibility to pay the benefits to members using the insurance payments. The buy-in policy will be treated as a plan asset going forward until such time as the buy-in policy is converted to a buy-out policy, which is when individual insurance policies will be assigned to each member of the plan and the plan will no longer have legal responsibility to pay the benefits to the members. The data cleansing effort has been substantially completed and we expect to recognize a pre-tax pension settlement loss of approximately $20 million upon the pension obligation becoming irrevocably settled, the timing of which is uncertain. The timing of the conversion to a buy-out policy and related recognition of the estimated pension settlement loss has been impacted by a ruling from the High Court of Justice in the United Kingdom in the case of Virgin Media Limited v NTL Pension Trustees II Limited and Others (the "Virgin Media Case") related to certain amendments to UK pension plans. In April 2026, the UK government approved legislation to address industry wide issues resulting from the Virgin Media Case. This legislation will enable us to proceed with the conversion to a buy-out policy which is expected to be completed by the second quarter of 2027 at the latest.

The following table provides the components of net periodic benefit cost for the pension plans:


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Service cost	$	0.0	$	1.3	$	0.1	$	1.6
Interest cost	0.6		0.7		1.2		1.9
Expected return on plan assets	(0.5)		(0.5)		(1.0)		(1.3)
Amortization of net loss	0.3		0.2		0.5		0.6
Settlement	0.0		0.0		0.0		29.0
Net periodic benefit cost	$	0.4	$	1.7	$	0.8	$	31.8
Defined contribution plan expense	$	1.7	$	1.2	$	4.6	$	4.5

The entire disclosure for retirement benefits.

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Stock-based Compensation - Summary of Stock-Based Compensation Expense Recognized (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Share-Based Payment Arrangement [Abstract]
Selling, general and administrative expenses	$ 2.9	$ 1.7	$ 6.8	$ 8.3
Less related income tax benefit	0.6	0.6	1.7	2.6
Decrease in net income	$ 2.3	$ 1.1	$ 5.1	$ 5.7

Basis of Presentation and New Accounting Pronouncements (Policies)	6 Months Ended
	Jun. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation – The accompanying unaudited condensed consolidated financial statements and related disclosures have been prepared in accordance with accounting principles generally accepted in the United States applicable to interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments considered necessary for a fair presentation of Koppers Holdings Inc.’s and its subsidiaries’ (Koppers, Koppers Holdings, the Company, we or us) financial position and interim results as of and for the periods presented have been included. All such adjustments are of a normal recurring nature unless disclosed otherwise. Because our business is seasonal, results for interim periods are not necessarily indicative of those that may be expected for a full year. The Condensed Consolidated Balance Sheet as of December 31, 2025 has been summarized from the audited balance sheet contained in the Annual Report on Form 10-K as of and for the year ended December 31, 2025. Certain prior period amounts in the condensed consolidated financial statements and notes to the condensed consolidated financial statements have been reclassified to conform to the current period’s presentation. The financial information included herein should be read in conjunction with our audited consolidated financial statements and related notes included in our Annual Report on Form 10-K as of and for the year ended December 31, 2025.
New Accounting Pronouncements	New Accounting Pronouncements – In November 2024, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2024-03, Income Statement - Reporting Comprehensive Income (Topic 220): Expense Disaggregation Disclosures. This ASU requires the disaggregation of certain expenses into specific categories, such as purchases of inventory, employee compensation, depreciation and intangible asset amortization. Additionally, the amendments require disclosure of the total amount of selling expenses and an annual disclosure of the definition of selling expenses. ASU No. 2024-03 is effective for fiscal years beginning after December 15, 2026 and for interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. The amendments should be applied either prospectively to financial statements issued for reporting periods after the effective date of this ASU or retrospectively to any and all prior periods presented in the financial statements. We are currently evaluating this ASU to determine its impact on our disclosures.

Derivative Financial Instruments - Summary of Unrealized (Gain) Loss from Hedging Contracts Where Hedge Accounting Was Not Elected (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Copper Swap Contracts
Derivative [Line Items]
(Gain) loss from contracts where hedge accounting was not elected	$ (2.1)	$ 0.6	$ (9.4)	$ 9.6
Heating Oil Contracts
Derivative [Line Items]
(Gain) loss from contracts where hedge accounting was not elected	(0.8)	0.0	2.6	0.2
Foreign currency forward contracts
Derivative [Line Items]
(Gain) loss from contracts where hedge accounting was not elected	$ 0.0	$ 0.1	$ (0.1)	$ 0.6

Earnings and Dividends per Common Share - Summary of Computation of Basic and Diluted Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Earnings Per Share [Abstract]
Net (loss) income	$ (147.5)	$ 16.4	$ (140.4)	$ 2.5
Weighted average common shares outstanding (in thousands):
Basic (in shares)	19,128	19,883	19,338	20,123
Effect of dilutive securities (in shares)	0	352	0	333
Diluted (in shares)	19,128	20,235	19,338	20,456
(Loss) earnings per common share:
Basic (in dollars per share)	$ (7.71)	$ 0.83	$ (7.26)	$ 0.13
Diluted (in dollars per share)	$ (7.71)	$ 0.81	$ (7.26)	$ 0.12
Antidilutive securities excluded from computation of diluted earnings per common share (in shares)	701,000	714,000	715,000	771,000

Debt

6 Months Ended

Jun. 30, 2026

Debt Disclosure [Abstract]

Debt


	Weighted Average Interest Rate		Maturity	June 30, 2026		December 31, 2025
(Dollars in millions)
Credit Facility	5.56	%	2030	$	427.0	$	448.0
Term Loan B	6.15	%	2030	478.7		480.3
Total debt				$	905.7	$	928.3
Less current maturities of long-term debt				4.9		4.9
Less unamortized debt issuance costs				8.1		9.1
Long-term debt				$	892.7	$	914.3

Credit Facility – We have a credit agreement (the Credit Facility) with a consortium of banks. The Credit Facility provides for an $800.0 million revolving credit facility, a $50.0 million swingline facility and provides for the ability to incur one or more uncommitted incremental revolving or term loan facilities in an aggregate amount of at least $730.0 million, subject to applicable financial covenants. The interest rate on the Credit Facility is variable and may be based on the SOFR, which is the applicable benchmark for current borrowings, or an alternative benchmark depending on the borrowing type.

Borrowings under the Credit Facility are secured by a first priority lien on substantially all of the assets (excluding real property and other customary assets) of Koppers Inc., Koppers Holdings Inc. and our material domestic subsidiaries. The Credit Facility contains certain covenants that may limit Koppers Inc. and its restricted subsidiaries from taking certain actions. These limitations include, among others, restrictions on additional indebtedness, liens, dividends, investments, acquisitions, certain distributions, asset sales, transactions with affiliates and modifications to material documents, including organizational documents. In addition, such covenants may give rise to events of default upon the failure by Koppers Inc. and its restricted subsidiaries to meet certain financial ratios.

As of June 30, 2026, we had $350.0 million of unused revolving credit availability after restrictions from certain letter of credit commitments and other covenants. As of June 30, 2026, $7.3 million of commitments were utilized by outstanding letters of credit.

Term Loan B – In April 2023, we issued a class of senior secured term loans under the Credit Facility (the Term Loan B) which was upsized in April 2024, resulting in $488.0 million of aggregate net proceeds, before debt financing costs. The interest rate on the Term Loan B is variable and is based on, at our option, adjusted Term SOFR Rate or adjusted Daily Simple SOFR. The interest rate margins applicable to adjusted Term SOFR Rate or adjusted Daily Simple SOFR loans are 2.50 percent with a floor of 0.50 percent. A portion of the principal balance of the Term Loan B is repayable in quarterly installments on the last business day of each quarterly period in an amount equal to 0.25 percent of the principal amount, with the balance due at maturity on April 10, 2030.

Interest Rate Swaps – See Note 4 – Derivative Financial Instruments for discussion of the interest rate swap agreements, which effectively convert the variable rate to a fixed rate for a portion of our variable rate debt.

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

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Summary of Components of Inventories

Inventories (Tables)

6 Months Ended

Jun. 30, 2026

Inventory Disclosure [Abstract]


	June 30, 2026		December 31, 2025
(Dollars in millions)
Raw materials	$	320.1	$	351.6
Work in process	13.3		17.3
Finished goods	153.5		147.0
Total	$	486.9	$	515.9
Less revaluation to LIFO	101.2		104.7
Inventories, net	$	385.7	$	411.2

Fair Value Measurements

6 Months Ended

Jun. 30, 2026

Fair Value Disclosures [Abstract]

Fair Value Measurements

The following table presents the estimated fair values and the related carrying amounts of our financial instruments:


	June 30, 2026				December 31, 2025
	Fair Value		Carrying Value		Fair Value		Carrying Value
(Dollars in millions)
Assets - Investments and Other Assets	$	1.4	$	1.4	$	1.3	$	1.3
Liabilities - Debt (including current portion)	$	912.9	$	905.7	$	933.6	$	928.3

Investments and Other Assets – Represents the broker-quoted cash surrender value on universal life insurance policies. This asset is classified as Level 2 in the valuation hierarchy and is measured from values received from financial institutions.

Debt – The fair value of our long-term debt is estimated based on the market prices for the same or similar issuances or on the current rates offered to us for debt of the same remaining maturities (Level 2). The fair value of our Credit Facility approximates carrying value due to the variable rate nature of this instrument.

See Note 4 – Derivative Financial Instruments, for the fair value of our derivative financial instruments.

Segment Information - Summary of Segment Revenues for Significant Product Lines (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Segment Reporting [Line Items]
Net sales	$ 520.1	$ 504.8	$ 975.4	$ 961.3
Operating Segments
Segment Reporting [Line Items]
Net sales	520.1	504.8	975.4	961.3
Railroad and Utility Products and Services \| Operating Segments
Segment Reporting [Line Items]
Net sales	245.9	250.4	465.9	485.4
Railroad and Utility Products and Services \| Railroad treated products \| Operating Segments
Segment Reporting [Line Items]
Net sales	147.3	150.9	281.5	297.2
Railroad and Utility Products and Services \| Utility poles \| Operating Segments
Segment Reporting [Line Items]
Net sales	86.7	75.8	161.5	143.7
Railroad and Utility Products and Services \| Railroad infrastructure products and services \| Operating Segments
Segment Reporting [Line Items]
Net sales	11.9	23.7	22.9	44.5
Performance Chemicals \| Wood preservative products and other \| Operating Segments
Segment Reporting [Line Items]
Net sales	168.2	150.8	310.3	271.7
Carbon Materials and Chemicals \| Operating Segments
Segment Reporting [Line Items]
Net sales	106.0	103.6	199.2	204.2
Carbon Materials and Chemicals \| Pitch and related products \| Operating Segments
Segment Reporting [Line Items]
Net sales	75.0	74.4	145.2	139.6
Carbon Materials and Chemicals \| Carbon black feedstock and distillates \| Operating Segments
Segment Reporting [Line Items]
Net sales	22.9	14.4	36.7	28.6
Carbon Materials and Chemicals \| Naphthalene, phthalic anhydride, and other chemicals \| Operating Segments
Segment Reporting [Line Items]
Net sales	$ 8.1	$ 14.8	$ 17.3	$ 36.0

Segment Information - Summary of Tangible and Intangible Assets by Segments (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Segment Reporting [Line Items]
Segment assets:	$ 1,722.3	$ 1,886.8
Goodwill	329.1	329.4
Corporate
Segment Reporting [Line Items]
Segment assets:	26.2	36.0
Railroad and Utility Products and Services
Segment Reporting [Line Items]
Goodwill	156.5	156.4
Railroad and Utility Products and Services \| Operating Segments
Segment Reporting [Line Items]
Segment assets:	833.5	827.5
Performance Chemicals
Segment Reporting [Line Items]
Goodwill	172.6	173.0
Performance Chemicals \| Operating Segments
Segment Reporting [Line Items]
Segment assets:	557.5	536.6
Carbon Materials and Chemicals \| Operating Segments
Segment Reporting [Line Items]
Segment assets:	$ 305.1	$ 486.7

Amount of asset recognized for present right to economic benefit.

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Income Taxes - Summary of Income Taxes Reconciled with Federal Statutory Rate (Details)	6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025
Income Tax Disclosure [Abstract]
Federal income tax rate	21.00%	21.00%
Foreign earnings taxed at different rates	(2.80%)	5.50%
Nondeductible expenses	(1.10%)	2.20%
State income taxes, net of federal tax benefit	1.00%	1.90%
Change in tax contingency reserves	(0.20%)	0.30%
U.S. tax on international operations, net of credits	0.00%	0.70%
Estimated annual effective income tax rate	17.90%	31.60%

CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS - USD ($) shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Income Statement [Abstract]
Net sales	$ 520.1	$ 504.8	$ 975.4	$ 961.3
Cost of sales	411.1	390.6	779.8	741.3
Depreciation and amortization	17.9	18.0	37.3	36.0
Selling, general and administrative	40.9	39.5	82.6	80.6
Impairment and restructuring	215.8	17.6	223.6	37.6
Loss (gain) on sale of assets	0.4	(0.0)	(3.9)	(0.3)
Operating (loss) profit	(166.0)	39.1	(144.0)	66.1
Other income, net	1.0	2.1	1.9	3.5
Interest expense	15.0	17.3	30.0	33.9
Loss on pension settlement	(0.0)	(0.0)	(0.0)	29.0
(Loss) income before income taxes	(180.0)	23.9	(172.1)	6.7
Income tax (benefit) provision	(32.5)	7.5	(31.7)	4.2
Net (loss) income	$ (147.5)	$ 16.4	$ (140.4)	$ 2.5
(Loss) earnings per common share:
Basic (in dollars per share)	$ (7.71)	$ 0.83	$ (7.26)	$ 0.13
Diluted (in dollars per share)	$ (7.71)	$ 0.81	$ (7.26)	$ 0.12
Weighted average shares outstanding (in thousands):
Basic (in shares)	19,128	19,883	19,338	20,123
Diluted (in shares)	19,128	20,235	19,338	20,456

Pensions and Post-Retirement Benefit Plans - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Pension settlement loss			$ 20.0
United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Premium payment			$ 67.8
US Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Pension liabilities		$ 84.5
Additional cash funding		$ 12.0
Pension settlement loss	$ 29.0

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Share-Based Payment Arrangement [Abstract]

CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Statement of Comprehensive Income [Abstract]
Tax (expense) benefit, cash flow hedges, net	$ 0.2	$ (0.6)	$ (0.0)	$ (2.0)
Pension adjustments, tax benefit	$ 0.0	$ 0.0	$ 0.0	$ 8.3

Stock-based Compensation

6 Months Ended

Jun. 30, 2026

Stock-based Compensation

The board of directors granted restricted stock units and performance stock units (collectively, the stock units) to certain employee participants in 2026. Most grants of restricted stock units vest in three or four years. Performance stock units vest based upon either a performance condition or a market condition. For units granted in 2025 and prior, performance stock units granted with a performance condition have a cumulative three-year performance objective based on adjusted EBITDA (see Note 7 – Segment Information). For units granted in 2026, performance stock units granted with a performance condition have a cumulative adjusted earnings per share objective and a cumulative free cash flow objective, each weighted at 50 percent, with adjusted EBITDA margin used as a performance modifier (i.e. plus or minus 25 percent of actual earned performance). For performance stock units granted with a market condition, the applicable objective is based on our total shareholder return relative to the Standard & Poor’s SmallCap 600 Materials Index and has multi-year performance objectives. Both types of performance stock units have a three-year period for vesting, if the applicable performance objectives are achieved.

The number of performance stock units granted represents the target award and participants have the ability to earn between zero and 200 percent of the target award based upon actual performance for units granted in 2025 and prior, and between zero and 250 percent of the target award based upon actual performance for units granted in 2026. If minimum performance criteria are not achieved, no performance stock units will vest. For the awards granted in 2026, target shares for units with a market condition totaled 129,843 and target shares for units with a performance condition totaled 142,383.

We calculated the fair value of the performance stock unit awards with a market condition on the date of the grant using assumptions listed below. These awards incorporate a fair value cap such that the number of awards that vest will be reduced if our stock price exceeds the cap at the end of the performance measurement period:


	January 2026 Grant			May 2026 Grant
Grant date price per share of performance award	$	26.93		$	41.54
Expected volatility	37.74		%	39.03		%
Risk-free interest rate	3.53		%	4.06		%
Look-back period in years	3.00			3.00

Grant date fair value per share	$	27.97		$	68.25

The following table shows a summary of the status and activity of non-vested stock units:


	Restricted Stock Units	Performance Stock Units	Total Stock Units	Weighted Average Grant Date Fair Value per Unit
Non-vested at December 31, 2025	530,237	734,231	1,264,468	$	35.22
Granted	256,608	272,652	529,260	$	28.77
Credited from dividends	379	643	1,022	$	28.28
Performance share adjustment	0	28,505	28,505	$	28.93
Vested	(250,920)	(329,924)	(580,844)	$	33.24
Forfeited	(24,882)	(17,187)	(42,069)	$	36.14
Non-vested at June 30, 2026	511,422	688,920	1,200,342	$	33.17

The following table shows a summary of the status and activity of stock options:


	Options	Weighted Average Exercise Price per Option		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2025	507,130	$	28.62
Exercised	(77,409)	$	20.25
Expired	(6,664)	$	32.19
Outstanding at June 30, 2026	423,057	$	30.10	3.37	$	6.3
Exercisable at June 30, 2026	423,057	$	30.10	3.37	$	6.3

The following table presents total stock-based compensation expense recognized in the condensed consolidated statement of operations:


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Selling, general and administrative expenses	$	2.9	$	1.7	$	6.8	$	8.3
Less related income tax benefit	0.6		0.6		1.7		2.6
Decrease in net income	$	2.3	$	1.1	$	5.1	$	5.7

Derivative Financial Instruments

6 Months Ended

Jun. 30, 2026

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Financial Instruments

We utilize derivative instruments to manage exposures to risks that have been identified, measured and are capable of being mitigated. The primary risks that we manage by using derivative instruments are commodity price risk associated with copper, fuel oil, foreign currency exchange risk and interest rate risk associated with variable rate borrowings. Generally, we enter into master netting arrangements with the counterparties and offset net derivative positions with the same counterparties. Currently, our agreements do not require cash collateral.

The Company recognizes all derivative instruments as either assets or liabilities at fair value on the balance sheet. The derivative instruments are classified as current or noncurrent based upon the expected timing of cash flows and are subject to offset under our master netting arrangements. A derivative instrument's fair value is determined using significant other observable inputs, a Level 2 fair value measurement.

For derivative instruments that are designated and qualify as cash flow hedges, the effective portion of the gain or loss on the derivative is reported as a component of other comprehensive income and is reclassified into earnings in the same period or periods during which the hedged transaction affects earnings. Gains and losses on the derivative instruments representing hedge ineffectiveness are recognized in current earnings. In our condensed consolidated statement of cash flows, settlements of derivative instruments are classified as operating activities.

Swap contracts on copper are used to manage the price risk associated with forecasted purchases of materials used in our manufacturing processes. Generally, we will not hedge cash flow exposures for durations longer than 36 months and we have hedged certain volumes of copper through the end of 2027. Prior to July 2025, we designated certain of our commodity swaps as cash flow hedges of forecasted purchases of commodities. For those commodity swaps where hedge accounting is not elected, the unrealized gain or loss on the derivative is reported as cost of sales in the condensed consolidated statement of operations.

During the third quarter of 2025, our quarterly effectiveness assessment identified that our hedging contracts had fallen outside the required effectiveness thresholds to continue cash flow hedge accounting. This was caused by the increased and cumulative volatility in the market prices for copper during the first half of 2025. Accordingly, we prospectively discontinued cash flow hedge accounting in the third quarter of 2025. As of June 30, 2026, $1.3 million remained in accumulated other comprehensive income and will be released to income as the underlying hedge contracts mature through December 2026. Subsequent changes in the fair value of these copper swap contracts will continue to be recognized immediately in earnings until such swap contracts settle or mature.

We enter into heating oil swap contracts to manage price risk associated with fuel oil purchases for our plant operations and certain raw material requirements. Generally, we will not hedge cash flow exposures for durations longer than 36 months and we have hedged certain volumes of heating oil through the end of 2027. These swap contracts are not designated as hedges so the unrealized gain or loss on the derivative is reported as cost of sales in the condensed consolidated statement of operations. As of June 30, 2026 and December 31, 2025, we had contracts totaling 2.9 million and 3.8 million gallons, respectively.

We enter into foreign currency forward contracts to manage foreign currency risk associated with our receivable and payable balances in addition to foreign-denominated sales. These forward contracts related to foreign currency are not designated as hedges so the unrealized gain or loss on the derivative is reported as cost of sales in the condensed consolidated statement of operations.

We enter into interest rate swaps to effectively convert portions of our variable interest rate debt into fixed rate debt to add stability to interest expense and to manage our exposure to interest rate movements. In 2023, we entered into interest rate swap agreements with an aggregate notional amount of $400.0 million at a weighted average fixed Secured Overnight Financing Rate (SOFR) of 3.97 percent. These swap agreements expire in April 2027. During the second quarter of 2026, we entered into forward-starting interest rate swap agreements that commence in April 2027. These swaps have aggregate notional amounts of $100.0 million, $150.0 million and $150.0 million, at a weighted average fixed SOFR of 4.10 percent, 4.01 percent and 3.99 percent, and expire in April 2028, April 2029 and April 2030, respectively. The interest rate swaps have been designated as cash flow hedges on interest payments involving the receipt of variable amounts from a counterparty in exchange for us making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount.

See the condensed consolidated statement of comprehensive income and condensed consolidated statement of shareholders' equity for amounts recorded in other comprehensive income and for amounts reclassified from accumulated other comprehensive income into net income.

The fair value of the outstanding derivative contracts recorded in the balance sheet are as follows:


			June 30, 2026
	Copper Swap Contracts		Heating Oil Contracts		Foreign Currency Forward Contracts		Interest Rate Swap Contracts		Total
(Dollars in millions)
Derivative contracts	$	20.8	$	1.7	$	0.0	$	0.7	$	23.2
Other assets	0.0		0.4		0.0		0.0		0.4
Accrued liabilities	0.0		0.0		(0.1)		(0.8)		(0.9)
Other long-term liabilities	(0.6)		0.0		0.0		(1.1)		(1.7)
Net asset (liability) on balance sheet	$	20.2	$	2.1	$	(0.1)	$	(1.2)	$	21.0
Accumulated other comprehensive gain, net of tax	$	1.7	$	0.0	$	0.0	$	0.9	$	2.6


			December 31, 2025
	Copper Swap Contracts		Heating Oil Contracts		Foreign Currency Forward Contracts		Interest Rate Swap Contracts		Total
(Dollars in millions)
Derivative contracts	$	31.4	$	0.0	$	0.0	$	0.1	$	31.5

Accrued liabilities	0.0		(0.4)		0.0		(2.2)		(2.6)
Other long-term liabilities	0.0		0.0		0.0		(1.1)		(1.1)
Net asset (liability) on balance sheet	$	31.4	$	(0.4)	$	0.0	$	(3.2)	$	27.8
Accumulated other comprehensive gain (loss), net of tax	$	2.5	$	0.0	$	0.0	$	(2.4)	$	0.1

We estimate that unrealized gains, net of tax, for commodity price hedging of $0.7 million and unrealized losses, net of tax, for interest rate swaps of $0.1 million, respectively, will be reclassified from other comprehensive income into earnings over the next twelve months.

The unrealized gain (loss) from our hedging contracts is as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Copper swap contracts	$	(2.1)	$	0.6	$	(9.4)	$	9.6
Heating oil contracts	(0.8)		0.0		2.6		0.2
Foreign currency forward contracts	0.0		0.1		(0.1)		0.6

Copper Swap Contracts – We had outstanding copper swap contracts of the following amounts:


	Units Outstanding (in Pounds)		Net Fair Value – Asset
	June 30, 2026	December 31, 2025	June 30, 2026		December 31, 2025
(Amounts in millions)

Not designated as hedges	26.8	25.6	$	20.2	$	31.4

Foreign Currency Forward Contracts – The net currency units outstanding for contracts were:


	June 30, 2026		December 31, 2025
(In millions)
Australian Dollars	AUD	3.2	AUD	0.0
British Pound Sterling	GBP	0.0	GBP	0.3
United States Dollars	USD	6.0	USD	9.2

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

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Commitments and Contingencies Disclosure [Abstract]

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Jun. 30, 2026
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Debt - Additional Information (Details) - USD ($)	1 Months Ended
Debt - Additional Information (Details) - USD ($)	Apr. 30, 2023	Jun. 30, 2026
Debt Instrument [Line Items]
Revolving credit facility		$ 730,000,000.0
Senior Secured Credit Facilities
Debt Instrument [Line Items]
Letters of credit, amount outstanding		7,300,000
Revolving Credit Agreement
Debt Instrument [Line Items]
Revolving credit facility		800,000,000.0
Swingline Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility		50,000,000.0
Credit Facility \| Senior Secured Credit Facilities
Debt Instrument [Line Items]
Debt instrument, unused borrowing capacity		$ 350,000,000.0
Amendment Number One to Credit Facility \| Term Loan B
Debt Instrument [Line Items]
Net proceeds from secured debt, before debt financing costs	$ 488,000,000.0
Amendment Number Two To Credit Facility \| Term Loan B
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.50%
Debt instrument, floor interest rate	0.50%
Debt instrument, percentage of principal payment	0.25%

Restructuring - Summary of Details of Plant Closures and Restructuring Liabilities (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2026	Dec. 31, 2025
Workforce reduction program
Restructuring Reserve [Roll Forward]
Balance at beginning of period	$ 0.6	$ 4.4
Accrual	0.0	1.2
Cash paid	(0.6)	(5.0)
Balance at end of period	0.0	0.6
Stickney Shutdown
Restructuring Reserve [Roll Forward]
Balance at beginning of period	0.0	0.0
Accrual	38.4	0.0
Cash paid	(0.0)	(0.0)
Balance at end of period	38.4	0.0
Short-term, asset retirement obligation	18.5
Phthalic Anhydride Shutdown
Restructuring Reserve [Roll Forward]
Balance at beginning of period	5.4	0.0
Accrual	1.3	13.5
Cash paid	(2.3)	(8.1)
Balance at end of period	$ 4.4	$ 5.4

Commitments and Contingent Liabilities (Tables)

6 Months Ended

Jun. 30, 2026

Summary of Changes in Accrued Liability for Environmental Matters

The following table reflects changes in the accrual for environmental remediation. As of June 30, 2026 and December 31, 2025, $1.6 million and $1.8 million, respectively, were classified as current liabilities.


	Period ended
	June 30, 2026		December 31, 2025
(Dollars in millions)
Balance at beginning of period	$	10.2	$	10.3
Expense	0.2		0.5
Cash expenditures	(0.3)		(0.4)
Revision of reserves	(0.1)		(0.3)
Currency translation	0.0		0.1
Balance at end of period	$	10.0	$	10.2

Debt - Summary of Long-Term Debt Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Debt Instrument [Line Items]
Total debt	$ 905.7	$ 928.3
Less current maturities of long-term debt	4.9	4.9
Less unamortized debt issuance costs	8.1	9.1
Long-term debt	$ 892.7	914.3
Term Loan B
Debt Instrument [Line Items]
Weighted Average Interest Rate	6.15%
Total debt	$ 478.7	480.3
6.19 Percent Credit Facility \| Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate	5.56%
Total debt	$ 427.0	$ 448.0

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of unamortized debt discount (premium) and debt issuance costs.

+ References + Details

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

Restructuring and Related Activities [Abstract]

Restructuring

6 Months Ended

Jun. 30, 2026

Restructuring

Plant Closures and Restructuring – The following table summarizes restructuring activities:


	Three Months Ended June 30,				Six Months Ended June 30,				Cumulative Total
	2026		2025		2026		2025
(Dollars in millions)
Stickney Shutdown:
Severance, retention and employee benefits	$	2.0	$	0.0	$	2.0	$	0.0	$	2.0
Impairment	164.6		0.0		164.6		0.0		164.6
Depreciation and asset disposal costs	8.5		0.0		8.5		0.0		8.5
Plant cleaning, waste disposal and demolition costs	36.4		0.0		36.4		0.0		36.4
Phthalic Anhydride Shutdown:
Severance and employee benefits	0.0		0.5		0.1		0.6		1.1
Depreciation and asset disposal costs	0.2		4.6		0.2		18.5		26.8
Plant cleaning, waste disposal and demolition costs	0.9		7.9		1.3		7.9		14.7
Workforce reduction program	0.0		0.2		0.0		3.3		8.3
Consulting services	2.7		4.4		5.1		7.3		21.0
Other restructuring costs	0.5		0.0		5.4		0.0		9.0
Total impairment and restructuring	$	215.8	$	17.6	$	223.6	$	37.6	$	292.4

Stickney Shutdown – We have made the decision to discontinue distillation and chemical manufacturing operations at our Carbon Materials and Chemicals facility in Stickney, Illinois. The decision was driven by challenging market conditions over the past decade, including unit operating costs outpacing our ability to capture higher pricing, reduced raw material supply from North American steel manufacturers and increased capital requirements. We anticipate winding down the remaining distillation and chemical production activities by December 31, 2026 at the latest and are tentatively targeting fourth quarter 2026 for shifting production to our coal tar distillation facility located in Nyborg, Denmark. We continue to evaluate potentially appropriate uses for the Stickney facility following the end of production activities.

Phthalic Anhydride Shutdown – In December 2024, we made the decision to discontinue phthalic anhydride production at our Carbon Materials & Chemicals facility in Stickney, Illinois. The decision was driven by significant near-term capital spending requirements that could not be economically justified by end-market projections and will substantially reduce annual emissions of certain regulated air contaminants. During the second quarter of 2025, we completed the shutdown of the phthalic anhydride plant.

We expect these combined actions to result in the following cumulative charges, which includes the amounts already spent in the above table:


Expected Totals	Low		High
(Dollars in millions)
Severance, retention and employee benefits (cash)	$	5.0	$	5.0
Impairment, depreciation and asset disposal costs (non-cash)	176.0		185.0
Plant cleaning, waste disposal and demolition costs (cash)	52.0		62.0
Stickney Shutdown Total Pre-tax Charges	$	233.0	$	252.0

Severance, retention and employee benefits (cash)	$	1.0	$	1.0
Depreciation and asset disposal costs (non-cash)	28.0		28.0
Plant cleaning, waste disposal and demolition costs (cash)	21.0		25.0
Phthalic Anhydride Shutdown Total Pre-tax Charges	$	50.0	$	54.0

Total Cash Charges	$	79.0	$	93.0
Total Non-Cash Charges	$	204.0	$	213.0

Workforce Reduction Program – In November 2024, we committed to a workforce reduction program across select U.S. locations, which is intended to streamline operations and reduce costs. This workforce reduction program resulted in the reallocation of people and resources, included voluntary and involuntary reductions in employees and ended in the fourth quarter of 2025.

Consulting Services – We have incurred and will continue to incur consulting and other professional service fees starting with a comprehensive assessment of each of our businesses and functions which began in the fourth quarter of 2024 and was completed during the third quarter of 2025. We then started the multi-year company-wide transformative project to design and implement changes that we believe will enable us to reach our full potential and improve profitability, modernize business processes and pursue portfolio realignment, if necessary.

Other Restructuring Costs – In the first quarter of 2026, we announced plans to idle two of our facilities. Consolidating production of these facilities will help us optimize our network, better align capacity with demand, reduce operating costs and strengthen the long-term competitiveness of our operations.

We made the decision to idle production activities at our Utility and Industrial Products facility in Vance, Alabama, effective in February 2026. Substantially all production handled at this location was transitioned to our Kennedy, Alabama plant. These facilities were located within 60 miles of each other and served the same market which resulted in plant underutilization, redundancy and higher operating costs.

We also announced our plan to idle production activities at our Railroad Products and Services facility in Florence, South Carolina due to lower overall future forecasted demand from the facility's largest customer. We expect to ramp down production at Florence over the next several months with plant idling activities to be completed by November 2026. During this time period, we will transition incremental production to our facility in Guthrie, Kentucky.

The following table includes details of our Stickney shutdown, phthalic anhydride shutdown and workforce reduction program liabilities:


	Stickney Shutdown		Phthalic Anhydride Shutdown		Workforce Reduction Program
(Dollars in millions)
Liability at December 31, 2024	$	0.0	$	0.0	$	4.4
Accrual	0.0		13.5		1.2
Cash paid	0.0		(8.1)		(5.0)
Liability at December 31, 2025	$	0.0	$	5.4	$	0.6
Accrual(1)	38.4		1.3		0.0
Cash paid	0.0		(2.3)		(0.6)
Liability at June 30, 2026	$	38.4	$	4.4	$	0.0

(1)Approximately $18.5 million of the Stickney shutdown accrual is a short-term asset retirement obligation, which is included in accrued liabilities in the condensed consolidated balance sheet.

KCCC Liquidation – In July 2024, Koppers and Tangshan Iron & Steel Group Co. Ltd. (TISCO) signed an agreement to effectuate the ultimate liquidation of Koppers (China) Carbon & Chemical Company Limited (KCCC), which ceased operations in 2015. The liquidation of KCCC was completed in February 2026 which resulted in a non-cash gain of approximately $4 million during the first quarter of 2026.

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025
Cash provided by (used in) operating activities:
Net (loss) income	$ (140.4)	$ 2.5
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	37.3	36.0
Impairment and depreciation in impairment and restructuring	209.7	18.0
Stock-based compensation	6.8	8.3
Change in derivative contracts	6.9	(9.8)
Non-cash interest expense	1.9	1.9
(Gain) on sale of assets	(3.8)	(1.0)
Insurance proceeds	(0.0)	(2.2)
Deferred income taxes	(36.7)	1.0
Pension settlement	(0.0)	29.0
Change in other liabilities	(1.8)	3.0
Cloud-based software implementation costs, net of amortization	0.2	(2.4)
Other - net	(0.4)	(1.4)
Changes in working capital:
Accounts receivable	(48.2)	(14.1)
Inventories	19.2	9.5
Accounts payable	44.5	(13.3)
Accrued liabilities	5.0	(34.3)
Other working capital	(3.9)	(2.9)
Net cash provided by operating activities	96.3	27.8
Cash (used in) provided by investing activities:
Capital expenditures	(23.7)	(26.4)
Insurance proceeds	0.0	2.2
Sale of assets	0.0	2.5
Sale of business and divestitures	0.5
Sale of business and divestitures		(7.6)
Other investing activities	0.8	(10.0)
Net cash (used in) investing activities	(22.4)	(39.3)
Cash (used in) provided by financing activities:
Borrowings of credit facility	358.4	271.5
Repayments of credit facility	(379.4)	(231.8)
Repayments of long-term debt	(2.5)	(2.5)
Issuances of Common Stock	0.5	0.6
Repurchases of Common Stock	(43.9)	(29.2)
Payment of debt issuance costs	(0.0)	(2.1)
Dividends paid and return of capital to noncontrolling interests	(3.8)	(3.2)
Net cash (used in) provided by financing activities	(70.7)	3.3
Effect of exchange rate changes on cash	(0.5)	2.7
Net increase (decrease) in cash and cash equivalents	2.7	(5.5)
Cash and cash equivalents at beginning of period	38.0	43.9
Cash and cash equivalents at end of period	40.7	38.4
Supplemental disclosure of non-cash investing and financing activities:
Right-of-use assets obtained in exchange for new operating lease liabilities	15.8	23.3
Accrued capital expenditures	$ 0.8	$ 2.4

CONDENSED CONSOLIDATED BALANCE SHEET (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Statement of Financial Position [Abstract]
Accounts receivable, allowance	$ 4.6	$ 7.0
Property, plant and equipment, accumulated depreciation	$ 646.6	$ 465.4
Senior Convertible Preferred Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Senior Convertible Preferred Stock, shares authorized (in shares)	10,000,000	10,000,000
Senior Convertible Preferred Stock, shares issued (in shares)	0	0
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized (in shares)	80,000,000	80,000,000
Common Stock, shares issued (in shares)	26,824,475	26,213,052
Treasury stock, shares (in shares)	7,920,741	6,757,247

CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (147.5)	$ 16.4	$ (140.4)	$ 2.5
Changes in other comprehensive (loss) income:
Currency translation adjustment	(0.7)	20.6	(6.5)	29.8
Cash flow hedges, net of tax of $0.2, $(0.6), $0.0 and $(2.0)	(0.7)	1.4	0.1	4.4
Pension adjustments, net of tax of $0.0, $0.0, $0.0 and $8.3	0.2	0.1	0.5	25.2
Comprehensive (loss) income	$ (148.7)	$ 38.5	$ (146.3)	$ 61.9

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

+ References + Details

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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Share-Based Payment Arrangement [Abstract]

Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2026

Summary of Stock Options And Performance Award Fair Value Assumptions


	January 2026 Grant			May 2026 Grant
Grant date price per share of performance award	$	26.93		$	41.54
Expected volatility	37.74		%	39.03		%
Risk-free interest rate	3.53		%	4.06		%
Look-back period in years	3.00			3.00

Grant date fair value per share	$	27.97		$	68.25

Summary of Status and Activity of Non-Vested Stock Units

The following table shows a summary of the status and activity of non-vested stock units:


	Restricted Stock Units	Performance Stock Units	Total Stock Units	Weighted Average Grant Date Fair Value per Unit
Non-vested at December 31, 2025	530,237	734,231	1,264,468	$	35.22
Granted	256,608	272,652	529,260	$	28.77
Credited from dividends	379	643	1,022	$	28.28
Performance share adjustment	0	28,505	28,505	$	28.93
Vested	(250,920)	(329,924)	(580,844)	$	33.24
Forfeited	(24,882)	(17,187)	(42,069)	$	36.14
Non-vested at June 30, 2026	511,422	688,920	1,200,342	$	33.17

Summary of Status and Activity of Stock Options

The following table shows a summary of the status and activity of stock options:


	Options	Weighted Average Exercise Price per Option		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2025	507,130	$	28.62
Exercised	(77,409)	$	20.25
Expired	(6,664)	$	32.19
Outstanding at June 30, 2026	423,057	$	30.10	3.37	$	6.3
Exercisable at June 30, 2026	423,057	$	30.10	3.37	$	6.3

Summary of Stock-based Compensation Expense Recognized

The following table presents total stock-based compensation expense recognized in the condensed consolidated statement of operations:


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Selling, general and administrative expenses	$	2.9	$	1.7	$	6.8	$	8.3
Less related income tax benefit	0.6		0.6		1.7		2.6
Decrease in net income	$	2.3	$	1.1	$	5.1	$	5.7

Derivative Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2026

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Summary of Fair Value of Outstanding Derivative contracts

The fair value of the outstanding derivative contracts recorded in the balance sheet are as follows:


			June 30, 2026
	Copper Swap Contracts		Heating Oil Contracts		Foreign Currency Forward Contracts		Interest Rate Swap Contracts		Total
(Dollars in millions)
Derivative contracts	$	20.8	$	1.7	$	0.0	$	0.7	$	23.2
Other assets	0.0		0.4		0.0		0.0		0.4
Accrued liabilities	0.0		0.0		(0.1)		(0.8)		(0.9)
Other long-term liabilities	(0.6)		0.0		0.0		(1.1)		(1.7)
Net asset (liability) on balance sheet	$	20.2	$	2.1	$	(0.1)	$	(1.2)	$	21.0
Accumulated other comprehensive gain, net of tax	$	1.7	$	0.0	$	0.0	$	0.9	$	2.6


			December 31, 2025
	Copper Swap Contracts		Heating Oil Contracts		Foreign Currency Forward Contracts		Interest Rate Swap Contracts		Total
(Dollars in millions)
Derivative contracts	$	31.4	$	0.0	$	0.0	$	0.1	$	31.5

Accrued liabilities	0.0		(0.4)		0.0		(2.2)		(2.6)
Other long-term liabilities	0.0		0.0		0.0		(1.1)		(1.1)
Net asset (liability) on balance sheet	$	31.4	$	(0.4)	$	0.0	$	(3.2)	$	27.8
Accumulated other comprehensive gain (loss), net of tax	$	2.5	$	0.0	$	0.0	$	(2.4)	$	0.1

Summary of Unrealized (Gain) loss from Contract Where Hedge Accounting Was Not Elected

The unrealized gain (loss) from our hedging contracts is as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions)
Copper swap contracts	$	(2.1)	$	0.6	$	(9.4)	$	9.6
Heating oil contracts	(0.8)		0.0		2.6		0.2
Foreign currency forward contracts	0.0		0.1		(0.1)		0.6

Summary of Outstanding Copper Swap Contracts

We had outstanding copper swap contracts of the following amounts:


	Units Outstanding (in Pounds)		Net Fair Value – Asset
	June 30, 2026	December 31, 2025	June 30, 2026		December 31, 2025
(Amounts in millions)

Not designated as hedges	26.8	25.6	$	20.2	$	31.4

Summary of Net Currency Units Outstanding

The net currency units outstanding for contracts were:


	June 30, 2026		December 31, 2025
(In millions)
Australian Dollars	AUD	3.2	AUD	0.0
British Pound Sterling	GBP	0.0	GBP	0.3
United States Dollars	USD	6.0	USD	9.2

Inventories

6 Months Ended

Jun. 30, 2026

Inventory Disclosure [Abstract]

Inventories


	June 30, 2026		December 31, 2025
(Dollars in millions)
Raw materials	$	320.1	$	351.6
Work in process	13.3		17.3
Finished goods	153.5		147.0
Total	$	486.9	$	515.9
Less revaluation to LIFO	101.2		104.7
Inventories, net	$	385.7	$	411.2

Earnings and Dividends per Common Share (Tables)

6 Months Ended

Jun. 30, 2026

Earnings Per Share [Abstract]

Summary of Computation of Basic and Diluted Earnings per Common Share

The following table sets forth the computation of basic and diluted earnings per common share:


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
(Dollars in millions, except share and per share amounts)
Net (loss) income	$	(147.5)	$	16.4	$	(140.4)	$	2.5
Weighted average common shares outstanding (in thousands):
Basic	19,128		19,883		19,338		20,123
Effect of dilutive securities	0		352		0		333
Diluted	19,128		20,235		19,338		20,456
(Loss) earnings per common share:
Basic	$	(7.71)	$	0.83	$	(7.26)	$	0.13
Diluted	$	(7.71)	$	0.81	$	(7.26)	$	0.12
Antidilutive securities excluded from computation of diluted earnings per common share	701		714		715		771

CONDENSED CONSOLIDATED BALANCE SHEET - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Assets
Cash and cash equivalents	$ 40.7	$ 38.0
Accounts receivable, net of allowance of $4.6 and $7.0	205.7	158.7
Inventories, net	385.7	411.2
Derivative contracts	23.2	31.5
Other current assets	24.3	29.3
Total current assets	679.6	668.7
Property, plant and equipment, net of accumulated depreciation of $646.6 and $465.4	482.1	650.9
Goodwill	329.1	329.4
Intangible assets, net	96.6	106.7
Operating lease right-of-use assets	103.6	102.9
Deferred tax assets	7.2	7.0
Other assets	24.1	21.2
Total assets	1,722.3	1,886.8
Liabilities
Accounts payable	166.0	122.4
Accrued liabilities	91.8	72.6
Current operating lease liabilities	28.7	27.2
Current maturities of long-term debt	4.9	4.9
Total current liabilities	291.4	227.1
Long-term debt	892.7	914.3
Operating lease liabilities	75.3	76.1
Accrued postretirement benefits	12.9	13.7
Deferred tax liabilities	7.4	43.7
Other long-term liabilities	55.6	37.6
Total liabilities	1,335.3	1,312.5
Commitments and contingent liabilities (Note 12)
Equity
Senior Convertible Preferred Stock, $0.01 par value per share; 10,000,000 shares authorized; no shares issued	0.0	0.0
Common Stock, $0.01 par value per share; 80,000,000 shares authorized; 26,824,475 and 26,213,052 shares issued	0.3	0.3
Additional paid-in capital	339.7	332.4
Retained earnings	395.0	539.4
Accumulated other comprehensive loss	(67.0)	(61.4)
Treasury stock, at cost, 7,920,741 and 6,757,247 shares	(281.0)	(236.7)
Total Koppers shareholders’ equity	387.0	574.0
Noncontrolling interests	0.0	0.3
Total equity	387.0	574.3
Total liabilities and equity	$ 1,722.3	$ 1,886.8

Debt (Tables)

6 Months Ended

Jun. 30, 2026

Debt Disclosure [Abstract]

Summary of Long-Term Debt Instruments


	Weighted Average Interest Rate		Maturity	June 30, 2026		December 31, 2025
(Dollars in millions)
Credit Facility	5.56	%	2030	$	427.0	$	448.0
Term Loan B	6.15	%	2030	478.7		480.3
Total debt				$	905.7	$	928.3
Less current maturities of long-term debt				4.9		4.9
Less unamortized debt issuance costs				8.1		9.1
Long-term debt				$	892.7	$	914.3

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

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