Metallus (MTUS) 10-K 28 Feb 24 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2023	Feb. 15, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Trading Symbol	MTUS
Title of 12(b) Security	Common shares
Security Exchange Name	NYSE
Entity Registrant Name	METALLUS INC.
Entity Central Index Key	0001598428
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Common Stock, Shares Outstanding		43,889,467
Entity Public Float			$ 903,279,470
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Document Financial Statement Error Correction [Flag]	false
ICFR Auditor Attestation Flag	true
Document Annual Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	OH
Entity Address, Address Line One	1835 Dueber Avenue SW
Entity Address, City or Town	Canton
Entity Address, State or Province	OH
City Area Code	330
Local Phone Number	471.7000
Entity Address, Postal Zip Code	44706
Entity Tax Identification Number	46-4024951
Entity File Number	1-36313
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Document Parts Into Which Incorporated Proxy Statement for the 2024 Annual Meeting of Shareholders Part III
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	Cleveland, Ohio

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Net sales	$ 1,362.4	$ 1,329.9	$ 1,282.9
Cost of products sold	1,175.9	1,203.2	1,062.9
Gross Profit	186.5	126.7	220
Selling, general and administrative expenses	84.6	73.8	77.2
Restructuring charges	0	0.8	6.7
Loss on sale of consolidated subsidiary	0	0	1.1
Loss (gain) on sale or disposal of assets, net	(2.5)	1.9	1.3
Impairment charges	0	0	10.6
Interest (income) expense, net	(7.1)	0.6	5.9
Loss on extinguishment of debt	11.4	43.1	0
Other (income) expense, net	3.7	(90.6)	(59.5)
Income (loss) from operations before income taxes	96.4	97.1	176.7
Provision (benefit) for income taxes	27	32	5.7
Net Income (Loss)	$ 69.4	$ 65.1	$ 171
Per Share Data:
Basic earnings (loss) per share	$ 1.58	$ 1.42	$ 3.73
Diluted earnings (loss) per share	$ 1.47	$ 1.3	$ 3.18

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ 69.4	$ 65.1	$ 171
Other comprehensive income (loss), net of tax of $0.2 million in 2023, $0.4 million in 2022, and none in 2021:
Foreign currency translation adjustments	0.3	(1.7)	0.3
Pension and postretirement liability adjustments	(2.6)	(4.3)	(20)
Other comprehensive income (loss), net of tax	(2.3)	(6)	(19.7)
Comprehensive Income (Loss), net of tax	$ 67.1	$ 59.1	$ 151.3

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Other comprehensive income (loss), net of tax	$ 0.2	$ 0.4	$ 0

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Current Assets
Cash and cash equivalents	$ 280.6	$ 257.2
Accounts receivable, net of allowances (2023 - $2.0 million; 2022 - $1.0 million)	113.2	79.4
Inventories, net	228	192.4
Deferred charges and prepaid expenses	10.3	6.4
Other current assets	24.7	21.2
Total Current Assets	656.8	556.6
Property, plant and equipment, net	492.5	486.1
Operating lease right-of-use assets	11.4	12.5
Pension assets	9.9	19.4
Intangible assets, net	2.7	5
Other non-current assets	2	2.4
Total Assets	1,175.3	1,082
Current Liabilities
Accounts payable	133.3	113.2
Salaries, wages and benefits	26.8	21.2
Accrued pension and postretirement costs	43.5	2
Current operating lease liabilities	5	6
Current convertible notes, net	13.2	20.4
Other current liabilities	26.6	23.9
Total Current Liabilities	248.4	186.7
Non-Current Liabilities
Credit Agreement	0	0
Non-current operating lease liabilities	6.4	6.5
Accrued pension and postretirement costs	160.5	162.9
Deferred income taxes	15	25.9
Other non-current liabilities	13.4	13.5
Total Liabilities	443.7	395.5
Shareholders’ Equity
Preferred shares, without par value; authorized 10.0 million shares, none issued	0	0
Common shares, without par value; authorized 200.0 million shares; issued 2023 - 47.1 million shares; issued 2022 - 47.1 million shares	0	0
Additional paid-in capital	844.2	847
Retained deficit	(53.7)	(123.1)
Treasury shares - 2023 - 4.0 million; 2022 - 3.0 million	(71.3)	(52.1)
Accumulated other comprehensive income (loss)	12.4	14.7
Total Shareholders’ Equity	731.6	686.5
Total Liabilities and Shareholders’ Equity	$ 1,175.3	$ 1,082

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Allowances for accounts receivable	$ 2	$ 1
Preferred shares, authorized (in shares)	10,000,000	10,000,000
Preferred shares, issued (in shares)	0	0
Common shares, authorized (in shares)	200,000,000	200,000,000
Common shares, issued (in shares)	47,100,000	47,100,000
Treasury Stock, Common, Shares	4,000,000	3,000,000

Consolidated Statements of Shar

Consolidated Statements of Shareholder's Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Shares	Additional Paid-in Capital	Additional Paid-in Capital Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings (Deficit)	Retained Earnings (Deficit) Cumulative Effect, Period of Adoption, Adjustment	Treasury Shares	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2020	$ 507.5			$ 843.4		$ (363.4)		$ (12.9)	$ 40.4
Beginning balance (in shares) at Dec. 31, 2020			45,164,308
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	171					171
Other comprehensive income (loss)	(19.7)								(19.7)
Stock-based compensation expense	7.3			7.3
Stock-based compensation expense (in shares)			272,462
Stock option activity	4.1			4.1
Stock options activity (in shares)			152,940
Issuance of treasury shares				(13.4)				13.4
Issuance of treasury shares (in shares)			638,093
Shares surrendered for taxes	(0.5)							(0.5)
Shares surrendered for taxes (in shares)			(72,174)
Convertible notes settlement	1.3			1.3
Convertible notes settlement (in shares)			113,226
Ending balance at Dec. 31, 2021	664.6	$ (6.4)		832.1	$ (10.6)	(188.2)	$ 4.2		20.7
Ending balance (in shares) at Dec. 31, 2021			46,268,855
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	65.1					65.1
Other comprehensive income (loss)	(6)								(6)
Stock-based compensation expense	8.8			8.8
Stock-based compensation expense (in shares)			342,805
Stock option activity	8			8
Stock options activity (in shares)			499,040
Purchase of treasury shares	(52)							(52)
Purchase of treasury shares (in Shares)			(3,026,491)
Issuance of treasury shares				(1.7)				1.7
Issuance of treasury shares (in shares)			97,475
Shares surrendered for taxes	(2)			(0.2)				(1.8)
Shares surrendered for taxes (in shares)			(116,793)
Ending balance at Dec. 31, 2022	686.5			847		(123.1)		(52.1)	14.7
Ending balance (in shares) at Dec. 31, 2022			44,064,891
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	69.4					69.4
Other comprehensive income (loss)	(2.3)								(2.3)
Stock-based compensation expense	11.5			11.5
Stock option activity	$ 2.8			2.8
Stock options activity (in shares)	291,928		322,074
Purchase of treasury shares	$ (32.9)			(0.3)				(32.6)
Purchase of treasury shares (in Shares)			(1,713,743)
Issuance of treasury shares				(16.8)				16.8
Issuance of treasury shares (in shares)			640,549
Shares surrendered for taxes	(3.4)							(3.4)
Shares surrendered for taxes (in shares)			177,460
Ending balance at Dec. 31, 2023	$ 731.6			$ 844.2		$ (53.7)		$ (71.3)	$ 12.4
Ending balance (in shares) at Dec. 31, 2023			43,136,311

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Activities
Net Income (Loss)	$ 69.4	$ 65.1	$ 171
Adjustments to reconcile net income (loss) to net cash provided (used) by operating activities:
Depreciation and amortization	56.9	58.3	63.1
Amortization of deferred financing fees	0.5	0.7	1
Loss on extinguishment of debt	11.4	43.1	0
Loss on sale of consolidated subsidiary	0	0	1.1
Loss (gain) on sale or disposal of assets, net	(2.5)	1.9	1.3
Impairment charges	0	0	10.6
Deferred income taxes	(9.7)	24.9	1.2
Stock-based compensation expense	11.5	8.8	7.3
Pension and postretirement expense (benefit), net	47.1	(40.5)	(38.7)
Changes in operating assets and liabilities:
Accounts receivable, net	(33.4)	21.3	(37.2)
Inventories, net	(34.9)	18.8	(41.6)
Accounts payable	15.3	(33.2)	53.5
Other accrued expenses	5.3	(8.8)	9.7
Deferred charges and prepaid expenses	(3.9)	(2.6)	0.1
Pension and postretirement contributions and payments	(2.8)	(5.4)	(6.9)
Other, net	(4.9)	(17.9)	1.4
Net Cash Provided (Used) by Operating Activities	125.3	134.5	196.9
Investing Activities
Capital expenditures	(51.6)	(27.1)	(12.2)
Proceeds from sale of consolidated subsidiary, net	0	0	6.2
Proceeds from disposals of property, plant and equipment	1.7	5.4	1.2
Net Cash Provided (Used) by Investing Activities	(49.9)	(21.7)	(4.8)
Financing Activities
Purchase of treasury shares	(32.6)	(52)	0
Proceeds from exercise of stock options	2.8	8	4.1
Shares surrendered for employee taxes on stock compensation	(3.4)	(2)	(0.5)
Repayments on convertible notes	(18.7)	(67.6)	(38.9)
Debt issuance costs	0	(1)	0
Net Cash Provided (Used) by Financing Activities	(51.9)	(114.6)	(35.3)
Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash	23.5	(1.8)	156.8
Cash and cash equivalents at beginning of period	257.8	259.6	102.8
Cash and Cash Equivalents at End of Period	$ 281.3	$ 257.8	$ 259.6

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 280.6	$ 257.2	$ 259.6
Restricted cash reported in other current assets	0.7	0.6	0
Total cash, cash equivalents, and restricted cash shown in the Consolidated Statements of Cash Flows	$ 281.3	$ 257.8	$ 259.6

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ 69.4	$ 65.1	$ 171

Insider Trading Arrangements

Insider Trading Arrangements - shares	3 Months Ended
	Dec. 31, 2023	Sep. 30, 2023
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		During the quarter ended December 31, 202 3, officers (as defined in Exchange Act Rule 16a-1(f)) of the Company adopted written plans for the sale of the Company’s common shares intended to satisfy the affirmative defense conditions of Exchange Act Rule 10b5-1(c) (“Rule 10b5-1 trading arrangements”) as follows: On November 14, 2023 , Nicholas A. Yacobozzi , Chief Accounting Officer , adopted a 10b5-1 trading arrangement that provides for the potential sale of up to 19,350 common shares that may be earned (net of shares withheld for taxes) upon the vesting of performance-based restricted stock units awarded for the 2021-2023 performance period, as well as up to 12,900 common shares expected to be received (net of shares withheld for taxes) upon vesting of restricted stock units on March 1, 2024, which trading arrangement is scheduled to terminate no later than August 25, 2024. Each of the above-named officers is currently and is expected to remain in compliance with his or her share ownership guidelines following the sale of any common shares pursuant to his or her 10b5-1 trading arrangement. Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year On February 26, 2024, the Company amended its existing Amended and Restated Articles of Incorporation, as amended (the “Amended Articles”), to revise Article FIRST to change its corporate name to “Metallus Inc.” The amendment was approved by the Company’s Board of Directors and was effected by the filing of a Certificate of Amendment to the Amended Articles with the Ohio Secretary of State. Also effective on February 26, 2024, the Company amended its existing Code of Regulations to reflect the new corporate name (the “Amended and Restated Regulations”). The Amended and Restated Regulations were approved by the Company’s Board of Directors. The foregoing descriptions are qualified in their entirety by reference to the Certificate of Amendment to the Amended Articles and the Amended and Restated Regulations, copies of which are attached as Exhibits 3.1 and 3.2, respectively, to this Annual Report on Form 10-K and are incorporated by reference herein.
Nicholas A. Yacobozz
Trading Arrangements, by Individual
Name	Nicholas A. Yacobozzi
Title	Chief Accounting Officer
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	November 14, 2023
Aggregate Available	19,350
Nicholas A. Yacobozzi Trading Arrangement Common Sale [Member] | Nicholas A. Yacobozz
Trading Arrangements, by Individual
Aggregate Available	12,900

Basis of Presentation

Basis of Presentation	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Note 1 - Basis of Presentation Metallus Inc. (the "Company" or "Metallus") manufactures alloy steel, as well as carbon and micro-alloy steel using electric arc furnace ("EAF") technology. Metallus' portfolio includes special bar quality ("SBQ") bars, seamless mechanical tubing ("tubes"), manufactured components, such as precision steel components, and billets. Additionally, Metallus manages raw material recycling programs, which are used internally as a feeder system for our melt operations and allow us to sell scrap not used in our operations to third parties. The Company’s products and services are used in a diverse range of demanding applications in the following end-markets: industrial, which includes industrial equipment, mining, construction, rail, heavy truck, agriculture and power generation; automotive; aerospace & defense; and energy. The SBQ bar, tube, and billet production processes take place at the Company’s Canton, Ohio manufacturing location. This location accounts for all of the SBQ bars, seamless mechanical tubes and billets the Company produces and includes three manufacturing facilities: the Faircrest, Harrison, and Gambrinus facilities. Metallus' production of manufactured components takes place at two downstream manufacturing facilities: Tryon Peak (Columbus, North Carolina) and St. Clair (Eaton, Ohio). Many of the production processes are integrated, and the manufacturing facilities produce products that are sold in all of the Company’s markets. As a result, investments in the Company’s facilities and resource allocation decisions affecting the Company’s operations are designed to benefit the overall business, not any specific aspect of the business. Our annual melt capacity is approximately 1.2 million tons and our shipment capacity is approximately 0.9 million tons. In addition to our internal melt capacity, the Company periodically purchases third party melt to supplement customer demand and leverage our downstream operations. Basis of Consolidation: The Consolidated Financial Statements include the consolidated assets, liabilities, revenues and expenses related to Metallus as of December 31, 2023, 2022 and 2021. All significant intercompany accounts and transactions within Metallus have been eliminated in the preparation of the Consolidated Financial Statements. Use of Estimates: The preparation of these Consolidated Financial Statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and accompanying notes. These estimates and assumptions are reviewed and updated regularly to reflect recent experience. Presentation: Certain items previously reported in specific financial statement captions have been reclassified to conform with current year presentation. In the fourth quarter of 2023, the Company split the aerospace & defense end-market out from the industrial end-market. These changes have been retrospectively applied. Refer to " Note 4 - Revenue Recognition" for further details.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Significant Accounting Policies	Note 2 - Significant Accounting Policies Revenue Recognition: Metallus recognizes revenue from contracts at a point in time when it has satisfied its performance obligation and the customer obtains control of the goods, at the amount that reflects the consideration the Company expects to receive for those goods. Substantially all performance obligations arise from the sale of manufactured steel products. The Company receives and acknowledges purchase orders from its customers, which define the quantity, pricing, payment and other applicable terms and conditions. In some cases, the Company receives a blanket purchase order from its customer, which includes pricing, payment and other terms and conditions, with quantities defined at the time the customer issues periodic releases from the blanket purchase order. Transfer of control and revenue recognition for substantially all the Company’s sales occur upon shipment or delivery of the product, which is when title, ownership, and risk of loss pass to the customer and is based on the applicable customer shipping terms. The Company invoices its customers at the time of title transfer. Payment terms are generally 30 days from the invoice date. Invoiced amounts are usually inclusive of shipping and handling activities incurred. Shipping and handling activities billed are included in net sales in the Consolidated Statements of Operations. The related costs incurred by the Company for the delivery of goods are classified as cost of products sold in the Consolidated Statements of Operations. Certain contracts contain variable consideration, which primarily consists of rebates that are accounted for in net sales and accrued based on the estimated probability of the requirements being met. Sales returns and allowances are treated as a reduction to net sales and are provided for primarily based on historical experience. These reserves also capture any potential warranty claims, which normally result in returned or replaced product. The Company’s contracts with certain Manufactured Components customers extend multiple years and generally average five years. While these contracts set the duration of time, they do not cover or guarantee volumes but rather are focused on piece prices, which are established at the inception of the contract. From time to time, subsequent pricing adjustments are agreed to through negotiation. Pricing adjustments are occasionally determined retroactively based on historical shipments. The Company recognizes revenue for these subsequent price adjustments when they are determined to be probable and estimable. For the year ended December 31, 2023, the Company recognized $ 16.0 million in subsequent pricing adjustments. Cash Equivalents and Restricted Cash: Metallus considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. The Company's restricted cash balance represents an imprest cash account used for the funding of employee healthcare costs. Funding of this account began during the first quarter of 2022 when the Company changed its healthcare plan administrator. The balance of restricted cash as of December 31, 2023 was $ 0.7 million, which is included in other current assets on the Consolidated Balance Sheets. The Company had $ 0.6 million of restricted cash as of December 31, 2022 . Accounts Receivables, Net: The Company’s accounts receivables arise from sales to customers across the industrial, automotive, aerospace & defense, and energy end markets. The allowance for doubtful account reserve has been established using qualitative and quantitative methods. In general, account balances are fully reserved when greater than one year of age or sent to third party collection. Account balances for customers that are viewed as higher risk are also analyzed for a reserve. In addition to these methods, the allowance for doubtful accounts is adjusted for forward-looking estimates of uncollectible balances based on end-market outlook and dynamics. Historically, write-offs for Metallus' allowance for doubtful accounts have been immaterial. Inventories, Net: Inventories are stated at lower of cost or net realizable value. All inventories, including raw materials, manufacturing supplies inventory, as well as international (outside the U.S.) inventories, have been valued using the FIFO or average cost method. Property, Plant and Equipment, Net: Property, plant and equipment, net are valued at cost less accumulated depreciation. Maintenance and repairs are charged to expense as incurred. The provision for depreciation is computed principally by the straight-line method based upon the estimated useful lives of the assets. The useful lives are approximately 30 years for buildings and 3 to 20 years for machinery and equipment. Impairment and Disposal of Long-lived Assets, Net: Long-lived assets (including property, plant and equipment, tangible assets and intangible assets subject to amortization) are reviewed for impairment when events or changes in circumstances have occurred indicating that the carrying value of the assets may not be recoverable. Metallus tests recoverability of long-lived assets at the lowest level for which there are identifiable cash flows that are independent from the cash flows of other assets. Assets and asset groups held and used are measured for recoverability by comparing the carrying amount of the asset or asset group to the sum of future undiscounted net cash flows expected to be generated by the asset or asset group. If an asset or asset group is considered to be impaired, the impairment loss that would be recognized is the amount by which the carrying amount of the assets exceeds the fair value of the assets. To determine fair value, Metallus uses internal cash flow estimates discounted at an appropriate interest rate, third party appraisals, as appropriate, and/or market prices of similar assets, when available. Refer to “Note 6 - Disposition of Non-Core Assets” and “Note 11 - Property, Plant and Equipment” for additional information. Income Taxes: Deferred tax assets and liabilities are recorded for the future tax consequences attributable to differences between financial statement carrying amounts of existing assets and liabilities and their respective tax bases, as well as net operating loss and tax credit carryforwards. Metallus accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. Metallus recognizes deferred tax assets to the extent Metallus believes these assets are more likely than not to be realized. In making such a determination, Metallus considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If Metallus determines that it would be able to realize deferred tax assets in the future in excess of their net recorded amount, Metallus would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. Metallus records uncertain tax positions in accordance with applicable accounting guidance, on the basis of a two-step process whereby (1) Metallus determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position, and (2) for those tax positions that meet the more-likely-than-not recognition threshold, Metallus recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. Metallus recognizes interest and penalties related to unrecognized tax benefits within the provision (benefit) for income taxes line in the accompanying Consolidated Statements of Operations, if applicable. Accrued interest and penalties are included within the related tax liability line in the Consolidated Balance Sheets. Pension and Other Postretirement Benefits: Metallus recogn izes an overfunded status or underfunded status (e.g., the difference between the fair value of plan assets and the benefit obligations) as either an asset or a liability for its defined benefit pension and other postretirement benefit plans on the Consolidated Balance Sheets. The Company recognizes actuarial gains and losses immediately through net periodic benefit cost in the Consolidated Statements of Operations upon the annual remeasurement at December 31, or on an interim basis as triggering events warrant remeasurement. An example of a potential triggering event would be settlements. The Company’s accounting policy is to recognize settlements during the quarter in which it is projected that the costs of all settlements during the year will be greater than the sum of the service cost and interest cost components of net periodic benefit cost. In addition, the Company uses fair value to account for the value of plan assets. Stock-Based Compensation: Metallus recognizes stock-based compensation expense based on the grant date fair value of the stock-based awards over their required vesting period on a straight-line basis, whether the awards were granted with graded or cliff vesting. Stock options are issued with an exercise price equal to the closing market price of Metallus common shares on the date of grant. The fair value of stock options is determined using a Black-Scholes option pricing model, which incorporates assumptions regarding the expected volatility, the expected option life, the risk-free interest rate and the expected dividend yield. Annual grants of performance-based restricted stock units vest based on achievement of a relative total shareholder return ("TSR") metric. The TSR metric is considered a market condition, which requires Metallus to reflect it in the fair value on grant date using an advanced option-pricing model. The fair value of each performance share was therefore determined using a Monte Carlo valuation model, a generally accepted lattice pricing model. The Monte Carlo valuation model, among other factors, uses commonly-accepted economic theory underlying all valuation models, estimates fair value using simulations of future share prices based on stock price behavior and considers the correlation of peer company returns in determining fair value. In the fourth quarter, the Board approved and authorized a performance-based Transformation Incentive Grant program (the “Transformation Incentive Grant Progra m”). Under the Transformation Incentive Grant Program, certain employees were granted performance-based Restricted Share Unit awards designed to be earned from 0 percent to 200 percent of target levels depending on the degree to which the closing price performance of the Company's common shares satisfies specific average per share closing price goals during a performance period running from December 1, 2023 through December 31, 2026. Shares earned, if any, will then pay out in two equal installments in early 2027 and 2028, generally conditioned on continued employment with the Company until the applicable vesting date. Similar to the annual performance-based restricted stock units, the fair value of each share is determined using a Monte Carlo valuation model, a generally accepted lattice pricing model. The fair value of stock-based awards that will settle in Metallus common shares, other than stock options and performance-based restricted stock units, is based on the closing market price of Metallus common shares on the grant date. Metallus recognizes all excess tax benefits and tax deficiencies as income tax expense or benefit in the Consolidated Statements of Operations. The excess tax benefits and tax deficiencies are considered discrete items in the reporting period they occur and are not included in the estimate of an entity’s annual effective tax rate. Adoption of New Accounting Standards The Company did not adopt any Accounting Standard Updates (“ASU”) during 2023. Accounting Standards Issued But Not Yet Adopted The Company has considered the recent ASU's issued by the Financial Accounting Standards Board summarized below: Standard Adopted Description Effective Date Impact ASU 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures The standard enhances income tax disclosures primarily related to the rate reconciliation and income taxes paid. Annual periods beginning after December 15, 2024 The Company is currently evaluating the impact of the adoption of this ASU on its results of operations and financial condition. ASU 2023-07, Segment Reporting - Improvements to Reportable Segment Disclosures The standard enhances reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. Annual periods beginning after December 15, 2023, and interim periods beginning after December 15, 2024 The Company is currently evaluating the impact of the adoption of this ASU on its results of operations and financial condition.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2023
Segment Reporting [Abstract]
Segment Information	Note 3 - Segment Information We conduct our business activities and report financial results as one business segment. The presentation of financial results as one reportable segment is consistent with the way the Company operates its business and is consistent with the manner in which the Chief Operating Decision Maker ("CODM") evaluates performance and makes resource and operating decisions for the business as described above. Furthermore, the Company notes that monitoring financial results as one reportable segment helps the CODM manage costs on a consolidated basis, consistent with the integrated nature of the operations. Geographic Information Net sales by geographic area are reported by the country in which the customer is domiciled. Long-lived assets include property, plant and equipment and intangible assets subject to amortization. Long-lived assets by geographic area are reported by the location of the Metallus operations to which the asset is attributed. Year Ended December 31, 2023 2022 2021 Net Sales: United States $ 1,239.4 $ 1,201.3 $ 1,166.1 Foreign 123.0 128.6 116.8 $ 1,362.4 $ 1,329.9 $ 1,282.9 December 31, 2023 2022 Long-lived Assets, net: United States $ 506.2 $ 503.0 Foreign 0.4 0.6 $ 506.6 $ 503.6

Revenue Recognition

Revenue Recognition	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Note 4 - Revenue Recognition The following table provides the major sources of revenue by end-market for the years ended December 31, 2023, 2022 and 2021: Year Ended December 31, 2023 2022 2021 Industrial $ 533.3 549.0 601.0 Automotive 531.9 539.1 527.9 Aerospace & Defense (1) 115.0 79.7 60.2 Energy 160.4 136.6 62.9 Other (2) 21.8 25.5 30.9 Total Net Sales $ 1,362.4 $ 1,329.9 $ 1,282.9 (1) “Aerospace & Defense” sales by end-market were previously included in "Industrial." (2) “Other” sales by end-market includes the Company’s scrap sales. The following table provides the major sources of revenue by product type for the years ended December 31, 2023, 2022 and 2021: Year Ended December 31, 2023 2022 2021 Bar $ 917.1 $ 887.4 $ 863.6 Tube 170.1 173.7 164.4 Manufactured components 253.4 243.3 224.0 Other (3) 21.8 25.5 30.9 Total Net Sales $ 1,362.4 $ 1,329.9 $ 1,282.9 (3) “Other” for sales by product type relates to the Company’s scrap sales. Contract liabilities are recognized when the Company has received consideration from a customer to transfer goods at a future point in time. Contract liabilities are primarily related to deferred revenue resulting from cash payments received in advance from customers and are included in other current liabilities on the Consolidated Balance Sheets. Contract liabilities totaled $ 0.8 million and $ 3.6 million as of December 31, 2023 and 2022, respectively.

Restructuring Charges

Restructuring Charges	12 Months Ended
	Dec. 31, 2023
Restructuring and Related Activities [Abstract]
Restructuring Charges	Note 5 - Restructuring Charges Over the past several years, Metallus has made numerous organizational changes to enhance profitable and sustainable growth. These Company-wide actions included the restructuring of its business support functions, the reduct ion of management layers throughout the organization and other domestic and international actions to further improve the Company’s overall cost structure. There were no restructuring charges for the year ended December 31, 2023. Restructuring charges for the years ended December 31, 2022, and 2021 totaled $ 0.8 million and $ 6.7 million, respectively. For the years ended December 31, 2022 and 2021, restructuring charges were primarily related to severance and employee-related benefits, as a result of continued organizational changes. The following is a summary of the restructuring reserve for the twelve months ended December 31, 2023 and 2022: Balance at December 31, 2021 $ 4.7 Expenses 0.8 Payments ( 5.0 ) Balance at December 31, 2022 $ 0.5 Expenses — Payments ( 0.5 ) Balance at December 31, 2023 —

Disposition of Non-Core Assets

Disposition of Non-Core Assets	12 Months Ended
	Dec. 31, 2023
Discontinued Operations and Disposal Groups [Abstract]
Disposition of Non-Core Assets	Note 6 - Disposition of Non-Core Assets TimkenSteel Material Services Facility During the first quarter of 2020, management completed its previously announced plan to close the Company’s TimkenSteel Material Services (“TMS”) facility in Houston and began selling the assets at the facility. Land and buildings of $ 4.3 million associated with TMS were classified as assets held for sale on the Consolidated Balance Sheets as of December 31, 2021. All of these assets were sold during the third quarter of 2022. Net cash proceeds of $ 2.8 million were received and a loss on sale of assets of $ 1.5 million was recognized on the Consolidated Statements of Operations during 2022. Small-Diameter Seamless Mechanical Tubing Machinery and Equipment In the third quarter of 2020, the Company informed customers that as of December 31, 2020 the Company would discontinue the commercial offering of specific small-diameter seamless mechanical tubing products. In the fourth quarter of 2022, the Company entered into an agreement to sell the machinery and equipment used in the manufacturing of these specific products. The Company recei ved down payments totaling $ 3.4 million, with $ 1.7 million received in 2022 and the remaining $ 1.7 million received in 2023. The final payment resulted in a gain on disposal of assets of $ 3.4 million in the second quarter of 2023. The gain, which has been recognized in the Consolidated Statement of Operations, was partially offset by write-offs of aged assets removed from service throughout 2023. Harrison Melt and Casting Assets On February 16, 2021, management announced a plan to indefinitely idle its Harrison melt and casting assets, which was completed in the first quarter of 2021. All of the Company’s melt and casting activities now take place at the Faircrest location. The Company’s rolling and finishing operations at Harrison were not impacted by this action. The Company recognized non-cash charges of $ 9.5 million related to the write-down of the associated Harrison melt and casting assets in the first quarter of 2021. These charges include $ 7.9 million related to the impairment of the associated machinery and equipment, which is classified as impairment charges on the Consolidated Statements of Operations, as well as a write-down of spare parts of $ 1.6 million, which is included in cost of products sold in the Consolidated Statements of Operations, as management determined there was no alternative use. The Company did not incur any cash expenditures related to these charges. TimkenSteel (Shanghai) Corporation Limited On March 31, 2021, the Company entered into an agreement pursuant to which Daido Steel (Shanghai) Co., Ltd. agreed to acquire all of the Company’s ownership interest in TimkenSteel (Shanghai) Corporation Limited in an all-cash transaction. The sale closed on July 30, 2021 and net cash proceeds of $ 6.2 million were received in the third quarter of 2021. As a result of this transaction, a loss on sale of consolidated subsidiary of $ 1.1 million was recognized on the Consolidated Statements of Operations during the third quarter of 2021. Metallus' consolidated financial statements include activity for TimkenSteel (Shanghai) Corporation Limited through July 30, 2021. Customer Program Early Termination During the fourth quarter of 2021, the Company received communication from a customer that two specific programs would end earlier than originally forecasted. There was machinery at the St. Clair facility designed for these programs, which had no alternative use. As such, the Company recognized impairment charges of $ 2.4 million for the year ended December 31, 2021. Related supplies inventory of $ 0.2 million was also written down, which is included in cost of products sold in the Consolidated Statements of Operations, as management determined there was no alternative use. Additionally, cash previously received from the customer as reimbursement for capital investment for these early terminated programs was amortized as an expense reduction over the term of the related programs. With the early end to these programs, the remaining amount of capital recovery to be recognized of $ 1.1 million was accelerated and recognized within cost of products sold on the Consolidated Statements of Operations during the fourth quarter of 2021. In the fourth quarter of 2022, the Company received a customer reimbursement related to the initial capital investment for these early terminated programs in the net amount of $ 4.3 million, which is included in cost of products sold in the Consolidated Statements of Operations.

Other (Income) Expense, net

Other (Income) Expense, net	12 Months Ended
	Dec. 31, 2023
Other Income and Expenses [Abstract]
Other (Income) Expense, net	Note 7 - Other (Income) Expense, net The following table provides the components of other (income) expense, net for the years ended December 31, 2023, 2022 and 2021: Year Ended December 31, 2023 2022 2021 Pension and postretirement non-service benefit (income) loss $ ( 4.6 ) $ ( 20.3 ) $ ( 37.2 ) Loss (gain) from remeasurement of benefit plans 40.6 ( 35.4 ) ( 20.1 ) Foreign currency exchange loss (gain) — ( 0.2 ) 0.1 Insurance recoveries ( 31.3 ) ( 34.5 ) — Sales and use tax refund ( 1.4 ) — ( 2.5 ) Miscellaneous (income) expense 0.4 ( 0.2 ) 0.2 Total other (income) expense, net $ 3.7 $ ( 90.6 ) $ ( 59.5 ) Non-service related pension and other postretirement benefit income, for all years, consists primarily of the interest cost, expected return on plan assets and amortization components of net periodic cost. The Company's Bargaining Unit Pension Plan ("Bargaining Plan"), Retirement Plan (“Salaried Plan”), and the Supplemental Pension Plan ("Supplemental Plan") each have a provision that permits employees to elect to receive their pension benefits in a lump sum upon retirement. In the first quarter of 2023, the cumulative cost of all lump sum payments was projected to exceed the sum of the service cost and interest cost components of net periodic pension cost for the Salaried Plan. As a result, the Company completed a full remeasurement of its pension obligations and plan assets associated with the Salaried Plan during each quarter of 2023. A net loss of $ 40.6 million from the remeasurement of these benefit plans was recognized for the year ended December 31, 2023 . This loss was driven by a $ 36.6 million increase in the pension liability primarily due to a decrease in discount rate, updated census data and updates to certain underlying assumptions, as well as a loss of $ 4.0 million due to investment losses on plan assets. A net gain of $ 35.4 million from the remeasurement of these benefit plans was recognized for the year ended December 31, 2022 . This gain was driven by a $ 359.9 million decrease in the pension liability primarily due to an increase in discount rates and a $ 2.7 million non-cash settlement related to the partial annuitization of the Bargaining Plan. This was partially offset by a loss of $ 327.2 million driven primarily by investment losses on plan assets and lump sum basis losses. A net gain of $ 20.1 million from the remeasurement of these benefit plans was recognized for the year ended December 31, 2021 . This gain was driven by a $ 55.7 million decrease in the pension liability primarily due to an increase in discount rates, partially offset by a loss of $ 35.6 million driven primarily by investment losses on plan assets. For more details on the aforementioned remeasurements, refer to “Note 15 - Retirement and Postretirement Plans.” During the second half of 2022, the Faircrest melt shop experienced unplanned operational downtime. During the fourth quarter of 2022, the Company recognized an insurance recovery of $ 33.0 million related to the 2022 unplanned downtime, of which $ 13.0 million was received in the fourth quarter of 2022 and $ 20.0 million was received in the first quarter of 2023. Additionally, during the third quarter of 2022, the Company recognized an insurance recovery of $ 1.5 million related to an unplanned outage at our Faircrest facility in November 2021. During 2023, the Company recognized insurance recoveries of $ 31.3 million related to the 2022 Faircrest melt shop unplanned downtime, of which $ 11.3 million was received during 2023 and $ 20.0 million was received in the first quarter of 2024. The 2022 insurance claims were closed as of the first quarter of 2024. During the fourth quarter of 2023, the Company received a commitment from the State of Ohio related to the overpayment of sales and use taxes for the period of January 1, 2020 through March 31, 2023. This resulted in a gain recognized of $ 1.4 million, net of related professional fees, for the year ended December 31, 2023. During the second quarter of 2021, the Company received a refund from the State of Ohio related to an overpayment of sales and use taxes for the period of October 1, 2016 through September 30, 2019. This resulted in a gain recognized of $ 2.5 million, net of related professional fees, for the year ended December 31, 2021.

Income Tax Provision

Income Tax Provision	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Tax Provision	Note 8 - Income Tax Provision Income (loss) from operations before income taxes, based on geographic location of the operations to which such earnings are attributable, is provided below. Years Ended December 31, 2023 2022 2021 United States $ 103.2 $ 108.5 $ 171.2 Non-United States ( 6.8 ) ( 11.4 ) 5.5 Income (loss) from operations before income taxes $ 96.4 $ 97.1 $ 176.7 The provision (benefit) for income taxes consisted of the following: Years Ended December 31, 2023 2022 2021 Current: Federal $ 30.4 $ 0.6 $ 0.2 State and local 6.1 5.7 3.7 Foreign 0.2 0.8 0.6 Total current tax expense (benefit) $ 36.7 $ 7.1 $ 4.5 Deferred: Federal $ ( 9.2 ) $ 24.2 $ 0.8 State and local ( 0.5 ) 0.7 0.3 Foreign — — 0.1 Total deferred tax expense (benefit) ( 9.7 ) 24.9 1.2 Provision (benefit) for incomes taxes $ 27.0 $ 32.0 $ 5.7 For the year ended December 31, 2023 , Metallus made $ 19.0 million in U.S. federal payments, $ 4.9 million in state and local tax payments, $ 1.4 million in foreign tax payments, and had refundable overpayments of $ 0.3 million related to U.S. federal, state, and local income taxes. For the year ended December 31, 2022 , the Company made $ 2.0 million in U.S. federal payments, $ 5.0 million in state and local tax payments, $ 0.2 million in foreign tax payments, and had refundable overpayments of $ 2.2 million related to U.S. federal, state, and local income taxes. The reconciliation between Metallus' effective tax rate on income (loss) from continuing operations and the statutory tax rate is as follows: Years Ended December 31, 2023 2022 2021 U.S. federal income tax provision (benefit) at statutory rate $ 20.2 $ 20.4 $ 37.1 Adjustments: State and local income taxes, net of federal tax benefit 4.2 8.4 4.1 Permanent differences 1.2 8.9 ( 0.2 ) Foreign earnings taxed at different rates — ( 3.6 ) ( 0.5 ) Valuation allowance 1.8 ( 2.5 ) ( 34.8 ) U.S. research tax credit ( 0.3 ) ( 0.6 ) — Other items, net ( 0.1 ) 1.0 — Provision (benefit) for income taxes $ 27.0 $ 32.0 $ 5.7 Effective tax rate 28.0 % 32.9 % 3.2 % Income tax expense includes U.S. and international income taxes. Except as required under U.S. tax law, U.S. income and foreign withholding taxes have not been recognized on the excess of the amount for financial reporting over the tax basis of investments in foreign subsidiaries that is indefinitely reinvested outside the U.S. This amount becomes taxable upon a repatriation of assets from the subsidiary or a sale or liquidation of the subsidiary. The permanent differences for the year ended December 31, 2023 are due to limitations on the tax deductibility of the loss on extinguishment of debt on the Convertible Senior Notes due 2025 and excess compensation. The effect of temporary differences giving rise to deferred tax assets and liabilities at December 31, 2023 and 2022 was as follows: Years Ended December 31, 2023 2022 Deferred tax liabilities: Depreciation $ ( 75.0 ) $ ( 81.4 ) Inventory — — Prepaid insurance ( 1.9 ) — Leases - right-of-use asset ( 2.8 ) ( 3.1 ) Deferred tax liabilities $ ( 79.7 ) $ ( 84.5 ) Deferred tax assets: Tax loss carryforwards $ 16.0 $ 20.5 Pension and postretirement benefits 46.8 35.5 Other employee benefit accruals 8.0 6.6 Lease liability 2.8 3.1 State decoupling 1.2 0.8 Accrued restructuring — 0.1 Capital loss carryforward 0.8 0.8 Intangible assets 0.1 0.2 Inventory 0.8 0.7 Allowance for doubtful accounts 0.5 0.3 Accrued legal — 2.0 Capitalized R&D 3.2 0.9 Other, net — 0.1 Deferred tax assets subtotal $ 80.2 $ 71.6 Valuation allowances ( 15.5 ) ( 13.0 ) Deferred tax assets 64.7 58.6 Net deferred tax assets (liabilities) $ ( 15.0 ) $ ( 25.9 ) As of December 31, 2023 and 2022, the Company had a net deferred tax liability of $ 15.0 million and $ 25.9 million, respectively, on the Consolidated Balance Sheets. As of December 31, 2023 , the Company had loss carryforwards in the UK totaling $ 59.5 million having various expiration dates. There are no federal loss carryforwards in the U.S.; however, there are $ 15.8 million in state and certain local loss carryforwards with various expiration dates. During 2016, operating losses generated in the U.S. resulted in a decrease in the carrying value of the Company’s U.S. deferred tax liability to the point that would result in a net U.S. deferred tax asset at December 31, 2016. In light of the Company's operating performance in the U.S. and current industry conditions, the Company assessed, based upon all available evidence at the time, and concluded that it was more likely than not that it would not realize a portion of its U.S. deferred tax assets. As such, the Company recorded a valuation allowance in 2016. Each reporting period we assess available positive and negative evidence and estimate if sufficient future taxable income will be generated to utilize the Company’s deferred tax assets. Due to Metallus' historical operating performance in the U.S., we have historically been limited in our ability to rely on other subjective evidence such as projections of our future profitability. However, as of December 31, 2022, based on consecutive years of profitability, utilization of the majority of previously generated loss carryforwards in the U.S., and forecasted future profitability, the Company released a portion of its U.S. valuation allowance. The Company maintained a domestic partial valuation allowance on a capital loss carryforward and certain state loss carryforwards that are expected to expire unused. Metallus has provided a valuation allowance on the aforementioned UK loss carryforward. The need to maintain valuation allowances against deferred tax assets in the U.S. and other affected countries may cause variability in the Company’s effective tax rate. The majority of Metallus' income taxes are derived from federal, domestic state and local taxes. As of December 31, 2023, 2022 and 2021 , the Company had no total gross unrecognized tax benefits, and no amounts which represented unrecognized tax benefits that would favorably impact Metallus' effective income tax rate in any future periods if such benefits were recognized. As of December 31, 2023 , Metallus does not anticipate a change in its unrecognized tax positions during the next 12 months. Metallus had no accrued interest and penalties related to uncertain tax positions as of December 31, 2023, 2022 and 2021. As of December 31, 2023 , the tax years 2020 to the present remain open to examination by the IRS.

Earnings (Loss) Per Share

Earnings (Loss) Per Share	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Earnings (Loss) Per Share	Note 9 - Earnings (Loss) Per Share Basic earnings (loss) per share is computed based upon the weighted average number of common shares outstanding. Diluted earnings (loss) per share is computed based upon the weighted average number of common shares outstanding plus the dilutive effect of common share equivalents calculated using the treasury stock method or if-converted method. For the Convertible Notes, the Company utilizes the if-converted method to calculate diluted earnings (loss) per share. Under the if-converted method, the Company adjusts net earnings to add back interest expense (including amortization of debt issuance costs) recognized on the Convertible Notes and includes the number of shares potentially issuable related to the Convertible Notes in the weighted average shares outstanding. Treasury stock, if any, is excluded from the denominator in calculating both basic and diluted earnings (loss) per share. Equity-based Awards Common share equivalents for shares issuable for equity-based awards amounted to 3.4 million shares for the year ended December 31, 2023. For the year ended December 31, 2023 , 0.4 million shares were excluded from the computation of diluted earnings (loss) per share, primarily related to options with exercise prices above the average market price of our common shares (i.e., “underwater” options), because the effect of their inclusion would have been anti-dilutive. The difference between the remaining 3.0 million shares and 0.9 million shares assumed purchased with potential proceeds for the year ended December 31, 2023, were included in the denominator of the diluted earnings (loss) per share calculation. Common share equivalents for shares issuable for equity-based awards amounted to 4.0 million shares for the year ended December 31, 2022. For the year ended December 31, 2022 , 0.8 million shares were excluded from the computation of diluted earnings (loss) per share, primarily related to options with exercise prices above the average market price of our common shares (i.e., “underwater” options), because the effect of their inclusion would have been anti-dilutive. The difference between the remaining 3.2 million shares and 1.1 million shares assumed purchased with potential proceeds for the year ended December 31, 2022, were included in the denominator of the diluted earnings (loss) per share calculation. Common share equivalents for shares issuable for equity-based awards amounted to 4.8 million shares for the year ended December 31, 2021. For the year ended December 31, 2021 , 1.8 million shares were excluded from the computation of diluted earnings (loss) per share, primarily related to options with exercise prices above the average market price of our common shares (i.e., “underwater” options), because the effect of their inclusion would have been anti-dilutive. The difference between the remaining 3.0 million shares and 1.3 million shares assumed purchased with potential proceeds for the year ended December 31, 2021, were included in the denominator of the diluted earnings (loss) per share calculation. Convertible Notes Common share equivalents for shares issuable upon the conversion of outstanding convertible notes of 1.9 million for the year ended December 31, 2023, were included in the computation of diluted earnings (loss) per share, as these shares would be dilutive. In the first quarter of 2023, the Company repurchased $ 7.5 m illion of outstanding principal related to the Convertible Notes. There were no repurchases related to the Convertible Notes during the remainder of 2023. These repurchases of Convertible Notes reduced weighted average diluted shares outstanding by approximately 0.7 million shares for the year ended December 31, 2023. Refer to “Note 14 – Financing Arrangements” for additional information on the Convertible Notes. During the first half of 2022, the Company repurchased $ 25.2 million of outstanding principal related to the Convertible Notes. These repurchases of Convertible Notes reduced weighted average diluted shares outstanding by 2.3 million shares for the year ended December 31, 2022. The following table sets forth the reconciliation of the numerator and the denominator of basic and diluted earnings (loss) per share for the years ended December 31, 2023, 2022 and 2021: Year Ended December 31, 2023 2022 2021 Numerator: Net income (loss), basic $ 69.4 $ 65.1 $ 171.0 Add convertible notes interest 1.0 1.9 4.1 Net income (loss), diluted $ 70.4 $ 67.0 $ 175.1 Denominator: Weighted average shares outstanding, basic 43.8 45.8 45.9 Dilutive effect of equity-based awards 2.1 2.1 1.7 Dilutive effect of convertible notes 1.9 3.6 7.4 Weighted average shares outstanding, diluted 47.8 51.5 55.0 Basic earnings (loss) per share $ 1.58 $ 1.42 $ 3.73 Diluted earnings (loss) per share $ 1.47 $ 1.30 $ 3.18

Inventories

Inventories	12 Months Ended
	Dec. 31, 2023
Inventory Disclosure [Abstract]
Inventories	Note 10 – Inventories The components of inventories as of December 31, 2023 and 2022 were as follows: December 31, 2023 2022 Manufacturing supplies $ 51.5 $ 36.9 Raw materials 17.5 23.9 Work in process 109.6 94.7 Finished products 50.1 37.4 Gross inventory 228.7 192.9 Allowance for inventory reserves ( 0.7 ) ( 0.5 ) Total inventories, net $ 228.0 $ 192.4

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Note 11 - Property, Plant and Equipment The components of property, plant and equipment, net as of December 31, 2023 and 2022 were as follows: December 31, 2023 2022 Land $ 11.2 $ 11.2 Buildings and improvements 429.2 414.6 Machinery and equipment 1,367.6 1,391.5 Construction in progress 59.3 30.8 Subtotal 1,867.3 1,848.1 Less allowances for depreciation ( 1,374.8 ) ( 1,362.0 ) Property, plant and equipment, net $ 492.5 $ 486.1 Total depreciation expense wa s $ 54.6 m illion, $ 55.5 million, and $ 59.8 million for the years ended December 31, 2023, 2022, and 2021, respectively . Depreciation expense for the year ended December 31, 2021 includes $ 1.5 million of accelerated depreciation related to the closure of TMS which was announced in the fourth quarter of 2019 and the discontinuation of specific small-diameter seamless mechanical tube manufacturing announced in the third quarter of 2020. There was no accelerated depreciation for the years ended December 31, 2023 and 2022. For the year ended December 31, 2023, the Company recorded a gain on sale and disposal of assets of $ 2.5 million primarily related to the sale of the small-diameter seamless mechanical tubing machinery and equipment, partially offset by assets removed from service. No impairment charges were recognized in 2023. For the year ended December 31, 2022, the Company recorded a loss on sale and disposal of assets of $ 1.9 million primarily related to the sale of the remaining land and buildings at the Company's former TMS facility, as well as the disposition of excess and aged assets. No impairment charges were recognized in 2022. For the year ended December 31, 2021, the Company recorded a net loss on sale of assets of $ 1.3 million related to the disposition of excess assets. During 2021, the Company also recorded approximately $ 10.6 million of impairment charges related to the indefinite idling of the Harrison melt and casting assets, the impairment of certain assets at our St. Clair facility due to the early termination of a customer program, and the disposition of assets at our former TMS facility. Supplemental cash flow information related to non-cash investing activity was as follows: Year Ended December 31, 2023 2022 2021 Accrued property, plant and equipment purchases $ 12.1 $ 10.6 $ 3.6

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	Note 12 - Intangible Assets The components of intangible assets, net as of December 31, 2023 and 2022 were as follows: December 31, 2023 December 31, 2022 Gross Accumulated Net Gross Accumulated Net Customer relationships $ 6.3 $ 6.3 $ — $ 6.3 $ 6.2 $ 0.1 Technology use 9.0 9.0 — 9.0 9.0 — Capitalized software 55.6 53.2 2.4 57.9 53.0 4.9 Total intangible assets $ 70.9 $ 68.5 $ 2.4 $ 73.2 $ 68.2 $ 5.0 Intangibl e assets subject to amortization are amortized using a straight-line method over their legal or estimated useful lives. The weighted average useful lives of the customer relationships, technology use and capitalized software intangible assets are 15 years, 15 years and 6 years, respectively. The weighted average useful life of total intangible assets is 8 years as of December 31, 2023. Amortization expense for intangible assets for the years ended December 31, 2023, 2022, and 2021 was $ 2.3 million, $ 2.8 million and $ 3.3 million, respectively. There were no material losses on disposal of intangible assets for the years ended December 31, 2023, 2022 and 2021. Based upon the intangible assets subject to amortization as of December 31, 2023, Metallus' estimated annual amortization for the five succeeding years is shown below (in millions): Year Amortization 2024 $ 1.3 2025 0.3 2026 0.2 2027 0.1 2028 0.1

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Leases	Note 13 - Leases The Company has operating leases primarily related to machinery and equipment, vehicles and information technology equipment. These leases have remaining lease terms of less th an one year to approximately five years , so me of which may include options to extend the lease for one or more years. Certain leases also include options to purchase the leased asset. As of December 31, 2023, the Company has no financing leases. The weighted average remaining lease term for our operating leases as of December 31, 2023 w as 3.1 years. Leases with an initial term of 12 months or less ("short-term leases") are not recorded on the balance sheet. Rather, the Company recognizes lease expense for these leases on a straight-line basis over the lease term in accordance with the applicable accounting guidance. For lease agreements entered into after the adoption of lease accounting guidance on January 1, 2019, the Company combines lease and non-lease components. The Company’s lease agreements do not contain material residual value guarantees or material restrictive covenants. The Company recorded lease cost for the years ended December 31, 2023, 2022 and 2021 as follows: Year Ended December 31, 2023 2022 2021 Operating lease cost $ 7.3 $ 6.7 $ 8.2 Short-term lease cost 0.8 0.9 0.7 Total lease cost $ 8.1 $ 7.6 $ 8.9 When available, the rate implicit in the lease is used to discount lease payments to present value; however, the Company’s leases generally do not provide a readily determinable implicit rate. Therefore, the incremental borrowing rate to discount the lease payments is estimated using market-based information available at lease commencement. The weighted average discount rate used to measure our operating lease liabilities as of December 31, 2023 and 2022 was 4.3 % and 3.1 %, respectively. Supplemental cash flow information related to leases was as follows: Year Ended December 31, 2023 2022 2021 Cash paid for amounts included in the measurement of operating lease liabilities $ 7.1 $ 6.7 $ 8.2 Right-of-use assets obtained in exchange for operating lease obligations $ 5.6 $ 4.5 $ 3.1 Future minimum lease payments under non-cancellable leases as of December 31, 2023 were as follows: 2024 $ 5.5 2025 3.2 2026 1.7 2027 1.3 After 2028 0.8 Total future minimum lease payments 12.5 Less amount of lease payment representing interest ( 1.1 ) Total present value of lease payments $ 11.4

Financing Arrangements

Financing Arrangements	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Financing Arrangements	Note 14 - Financing Arrangements The following table summarizes the current and non-current debt as of December 31, 2023 and 2022: December 31, 2023 2022 Credit Agreement $ — $ — Convertible Senior Notes due 2025 13.2 20.4 Total debt $ 13.2 $ 20.4 Less current portion of debt 13.2 20.4 Total non-current portion of debt $ — $ — Amended Credit Agreement On September 30, 2022, the Company, as borrower, and certain domestic subsidiaries of the Company, as subsidiary guarantors (the “Subsidiary Guarantors”), entered into a Fourth Amended and Restated Credit Agreement (the “Amended Credit Agreement”), with JPMorgan Chase Bank, N.A., as administrative agent (the “Administrative Agent”), and the lenders party thereto (collectively, the “Lenders”), which further amended and restated the Company’s secured Third Amended and Restated Credit Agreement, dated as of October 15, 2019. The Amended Credit Agreement provides for a $ 400.0 million asset-based revolving credit facility (the “Credit Facility”), including a $ 15.0 million sublimit for the issuance of commercial and standby letters of credit and a $ 40.0 million sublimit for swingline loans. Pursuant to the terms of the Amended Credit Agreement, the Company is entitled, on up to two occasions and subject to the satisfaction of certain conditions, to request increases in the commitments under the Amended Credit Agreement in the aggregate principal amount of up to $ 100.0 million, to the extent that existing or new lenders agree to provide such additional commitments. In addition to and independent of any increase described in the preceding sentence, the Company is entitled, subject to the satisfaction of certain conditions, to request a separate “first-in, last-out” tranche (the “Incremental FILO Tranche”) in an aggregate principal amount of up to $ 30.0 million with a separate borrowing base and interest rate margins, in each case, to be agreed upon among the Company, the Administrative Agent and the Lenders providing the Incremental FILO Tranche. The availability of borrowings under the Credit Facility is subject to a borrowing base calculation based upon a valuation of the eligible accounts receivable, inventory and machinery and equipment of the Company and the Subsidiary Guarantors, each multiplied by an applicable advance rate. The availability of borrowings may be further modified by reserves established from time to time by the Administrative Agent in its permitted discretion. The interest rate per annum applicable to loans under the Credit Facility will be, at the Company’s option, equal to either (i) the Alternate Base Rate (as defined in the Amended Credit Agreement) plus the applicable margin or (ii) the Adjusted Term SOFR Rate (as defined in the Amended Credit Agreement) plus the applicable margin. The applicable margin will be determined by a pricing grid based on the Company’s average quarterly availability. The Alternate Base Rate is subject to a 1.00 % floor, and the Adjusted Term SOFR Rate is subject to a 0.00 % floor. In addition, the Company will pay a 0.25 % per annum commitment fee on the average daily unused amount of the Credit Facility. The Credit Facility may be used to finance working capital, capital expenditures, certain permitted acquisitions and for other general corporate purposes. All of the indebtedness under the Credit Facility is guaranteed by the Company’s material domestic subsidiaries, as well as any other domestic subsidiary that the Company elects to make a party to the Amended Credit Agreement, and is secured by substantially all of the personal property of the Company and the Subsidiary Guarantors. The Credit Facility matures on September 30, 2027 . Prior to the maturity date, amounts outstanding are required to be repaid (without reduction of the commitments thereunder) from mandatory prepayment events from the proceeds of certain asset sales, equity or debt issuances or casualty events. The Amended Credit Agreement contains certain customary covenants, including covenants that limit the ability of the Company and its subsidiaries to, among other things, (i) incur or suffer to exist certain liens, (ii) make investments, (iii) incur or guaranty additional indebtedness (iv) enter into consolidations, mergers, acquisitions, sale-leaseback transactions and sales of assets, (v) make distributions and other restricted payments, (vi) change the nature of its business, (vii) engage in transactions with affiliates and (viii) enter into restrictive agreements, including agreements that restrict the ability to incur liens or make distributions. In addition, the Amended Credit Agreement requires the Company to maintain a minimum specified fixed charge coverage ratio on a springing basis if minimum availability requirements as specified in the Amended Credit Agreement are not maintained. The Amended Credit Agreement contains certain customary events of default. If any event of default occurs and is continuing, the Lenders would be entitled to take various actions, including the acceleration of amounts due under the Amended Credit Agreement, and exercise other rights and remedies. As of December 31, 2023, the amount available under the Amended Credit Agreement was $ 258.8 million, reflective of the Company’s asset borrowing base with no outstanding borrowings. Additionally, the Company is in compliance with all covenants outlined in the Amended Credit Agreement. Convertible Senior Notes due 2025 The Convertible Senior Notes due 2025 were issued pursuant to the provisions of the indenture dated May 31, 2016, as supplemented by a supplemental indenture dated December 15, 2020, which was filed with the Securities and Exchange Commission as an exhibit to a Form 8-K on December 15, 2020. The indentures contain a complete description of the terms of the Convertible Senior Notes due 2025. The key terms are as follows: Maturity Date: December 1, 2025 unless repurchased or converted earlier Interest Rate: 6.0 % cash interest per year Interest Payments Dates: June 1 and December 1 of each year, beginning on December 1, 2021 Initial Conversion Price: $ 7.82 per common share of the Company Initial Conversion Rate: 127.8119 common shares per $ 1,000 principal amount of Notes The principal amount of the Convertible Senior Notes due 2025 as of December 31, 2023 is $ 13.3 million. Transaction costs related to the Convertible Senior Notes due 2025 incurred upon issuance were $ 1.5 million. These costs are amortized to interest expense over the term of the notes. The Convertible Senior Notes due 2025 are convertible at the option of the holders in certain circumstances and during certain periods into the Company's common shares, cash, or a combination thereof, at the Company's election. The Indenture for the Convertible Senior Notes due 2025 provides that notes will become convertible during a quarter when the share price for 20 trading days during the final 30 trading days of the immediately preceding quarter was greater than 130 % of the conversi on price. This criterion was met during the fourth quarter of 2023 (and each preceding quarter of 2023) and as such the notes can be converted at the option of the holders beginning January 1 through March 31, 2024. Whether the notes will be convertible following such period will depend on if this criterion, or another conversion condition, is met in the future. As such, the Convertible Senior Notes due 2025 are classified as a current liability on the Consolidated Balance Sheets as of December 31, 2023. This criterion was also met as of December 31, 2022. To date, no holders have elected to convert their notes during any optional conversion periods. For details regarding all conversion mechanics and methods of settlement, refer to the Indenture for the Convertible Senior Notes due 2025 filed as an exhibit to a Form 8-K on December 15, 2020. The components of the Convertible Senior Notes due 2025 as of December 31, 2023 and 2022 were as follows: December 31, 2023 2022 Principal $ 13.3 $ 20.8 Less: Debt issuance costs, net of amortization ( 0.1 ) ( 0.4 ) Less: Debt discount, net of amortization — — Convertible Senior Notes due 2025, net $ 13.2 $ 20.4 In the first quarter of 2023, the Company repurchased a total of $ 7.5 million aggregate principal amount of its Convertible Senior Notes due 2025. Total cash paid to noteholders was $ 18.7 million. A loss on extinguishment of debt of $ 11.4 million was recognized, including a charge of $ 0.2 million for unamortized debt issuance costs related to the portion of debt extinguished, as well as the related transaction costs. In the first half of 2022, the Company repurchased a total of $ 25.2 million aggregate principal amount of its Convertible Senior Notes Due 2025. There were no repurchases related to the Convertible Notes during the second h alf of 2022. Total cash paid to noteholders was $ 67.6 million. A loss on extinguishment of debt was recognized of $ 43.0 million, including a charge of $ 0.6 million for unamortized debt issuance costs related to the portion of debt extinguished, as well as the related transaction costs. Fair Value Measurement The fair value of the Convertible Senior Notes due 2025 was approximately $ 41.5 million as of December 31, 2023 and $ 53.4 million as of December 31, 2022. The fair value of the Convertible Senior Notes due 2025, which falls within Level 2 of the fair value hierarchy as defined by applicable accounting guidance, is based on a valuation model primarily using observable market inputs and requires a recurring fair value measurement on a quarterly basis. Metallus' Credit Facility is variable-rate debt. As such, any outstanding carrying value is a reasonable estimate of fair value as interest rates on these borrowings approximate current market rates. This valuation falls within Level 2 of the fair value hierarchy and is based on quoted prices for similar assets and liabilities in active markets that are observable either directly or indirectly. There were no outstanding borrowings on the Credit Facility as of December 31, 2023, 2022, and 2021. Interest (income) expense, net The following table provides the components of interest (income) expense, net for the years ended December 31, 2023, 2022 and 2021: Year Ended December 31, 2023 2022 2021 Interest expense $ 2.7 $ 3.9 $ 6.2 Interest income ( 9.8 ) ( 3.3 ) ( 0.3 ) Interest (income) expense, net $ ( 7.1 ) $ 0.6 $ 5.9 Interest income primarily relates to interest earned on cash invested in a money market fund and deposits with financial institutions. As of December 31, 2023, the carrying value of the Company's money market investment was $ 139.7 million, which approximates the fair value. The Company had $ 209.5 million invested in a money market fund as of December 31, 2022 , and no cash invested in a money market fund as of December 31, 2021. The money market fund is a cash equivalent and is included in cash and cash equivalents on the Consolidated Balance She ets. The fund consists of highly liquid investments with an average maturity of three months or less and falls within Level 1 of the fair value hierarchy as defined by applicable accounting guidance. Additionally, as of December 31, 2023, the Company has $ 119.9 million of cash held in other accounts which generate interest income at a rate similar to the money market fund. The following table sets forth total interest expense recognized specifically related to the Convertible Notes: Year Ended December 31, 2023 2022 2021 Contractual interest expense $ 0.9 $ 1.7 $ 3.7 Amortization of debt issuance costs 0.1 0.1 0.4 Total $ 1.0 $ 1.8 $ 4.1 The total cash interest paid for the year ended December 31, 2023 , 2022, and 2021 was $ 2.1 million, $ 3.1 million and $ 5.1 million, respectively. Treasury Shares On December 20, 2021, the Company announced that its Board of Directors authorized a share repurchase program under which the Company may repurchase up to $ 50.0 million of its outstanding common shares. The share repurchase program is intended to return capital to shareholders while also offsetting dilution from annual equity compensation awards. The share repurchase program does not require the Company to acquire any dollar amount or number of shares and may be modified, suspended, extended or terminated by the Company at any time without prior notice. On November 2, 2022, the Board of Directors authorized an additional $ 75.0 million share repurchase program. This authorization reflects the continued confidence of the Board and senior leadership in the Company’s ability to generate sustainable through-cycle profitability while maintaining a strong balance sheet and cash flow. For the year ended December 31, 2023 , the Company repurchased approximately 1.7 million common shares in the open market at an aggregate cost of $ 32.6 million, which equates to an average repurchase price of $ 19.03 per share. As of December 31, 2023 , the Company had a balance of $ 40.4 million remaining under its share repurchase program. For the year ended December 31, 2022 , the Company repurchased approximately 3.0 million common shares in the open market at an aggregate cost of $ 52.0 million, which equates to an average repurchase price of $ 17.18 per share . The Company did no t repurchase shares during the year ended December 31, 2021. Subsequent to December 31, 2023 , the Company repurchased 0.1 million additional common shares in the open market at an aggregate cost of $ 1.2 million, which equates to an average repurchase price of $ 21.07 per share. As of February 15, 2024, the Company has $ 39.2 million remaining under its authorized share repurchase program.

Retirement and Postretirement P

Retirement and Postretirement Plans	12 Months Ended
	Dec. 31, 2023
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Retirement and Postretirement Plans	Note 15 - Retirement and Postretirement Plans Eligible employees, including certain employees in foreign countries, participate in the following Company-sponsored plans: Retirement Plan ("Salaried Plan"); Bargaining Unit Pension Plan ("Bargaining Plan"), Supplemental Pension Plan ("Supplemental Plan"), UK Pension Scheme ("Pension Scheme"), Mexico Pension Plan, and Postretirement Plans made up the Company's Bargaining Unit Welfare Benefit Plan for Retirees and Welfare Benefit Plan for Retirees. Bargaining Plan On October 29, 2021, the United Steelworkers ("USW") Local 1123 voted to ratify a new four-year contract (the “Contract”). The Contract is in effect until September 27, 2025 and resulted in several changes to the Bargaining Plan which increased the pension liability by $ 14.2 million in 2021. These plan amendments were recognized in other comprehensive income (loss) in 2021 and will be amortized as part of the pension net periodic benefit cost in future periods. The main change that drove the increase in the pension liability was the addition of a full lump sum form of payment for participants commencing benefits on or after January 1, 2022. In addition, the plan is now closed to new entrants effective January 1, 2022. On July 7, 2022, the Company entered into an agreement with The Prudential Insurance Company of America ("Prudential") to purchase an irrevocable group annuity contract and transfer approximately $ 256.2 million of pension obligations under the Bargaining Plan. In connection with the agreement, Prudential began paying benefits under the group annuity contract as of October 1, 2022 for a specified group of approximately 1,900 participants and beneficiaries who previously received payments from the Bargaining Plan. Benefits payable to these participants and beneficiaries were not reduced as a result of this transaction. Plan participants and beneficiaries not included in the transaction remain in the Bargaining Plan. The Company recorded a non-cash settlement gain of approximately $ 2.7 million in the third quarter of 2022 related to this partial plan annuitization. This settlement is a significant event which also required remeasurement of the Bargaining Plan during the third quarter. The transaction was funded directly by the assets of the Bargaining Plan and required no cash contribution from the Company. The timing and amount of future required pension contributions is significantly affected by asset returns and actuarial assumptions. Based on the results of the December 31, 2023 pension calculations, the Company estimates required Bargaining Plan contributions of approximately $ 40 million in 2024, with approximately $ 25 million of contributions required in the first quarter. Required future pension contribution timing and amounts are subject to significant change based on future investment performance, Company estimates and actuarial assumptions, as well as current funding laws. Salaried Plan During the fourth quarter of 2021, termination of the Salaried Plan was approved by the Company's Board of Directors. Participants were notified in January 2022 and the plan was terminated effective March 31, 2022 , subject to regulatory approval, which was received in the fourth quarter of 2023. The purchase of an irrevocable annuity contract from an insurance company is expected to occur in 2024 , after which time the insurance company selected will be responsible for all participant benefit payments. Supplemental Plan During the fourth quarter of 2019, the Company amended the Supplemental Plan, which provides for the payment of nonqualified supplemental pension benefits to certain salaried participants in the Salaried Plan. The amendment provided for the cessation of benefit accruals under the Supplemental Plan, effective as of December 31, 2020. Effective January 1, 2021, there were no new accruals of benefits, including with respect to service accruals and the final average compensation determination. Certain of the Company’s current and prior named executive officers are participants in the plan. Existing benefits under the plan, as of December 31, 2020, will otherwise continue in accordance with the terms of the plan. Postretirement Plans During the second quarter of 2019, the Company amended its Bargaining Unit Welfare Plan for Retirees related to moving Medicare-eligible retirees to an individual plan on a Medicare healthcare exchange. During the fourth quarter of 2019, the Company also amended its Welfare Benefit Plan for Retirees, under which certain retired salaried employees of the Company and its subsidiaries are eligible to receive a Company contribution for their medical and prescription drug benefits under the retiree welfare plan. The amendment eliminated the retiree medical subsidy, effective as of December 31, 2019, for all remaining active salaried participants who retire after December 31, 2019 (provided, however, that participants who were laid off on or before March 31, 2020 and who otherwise qualified for the retiree medical subsidy under the terms of the retiree welfare plan remained entitled to receive the retiree medical subsidy). Pension benefits earned are generally based on years of service and compensation during active employment. Metallus' funding policy is consistent with the funding requirements of applicable laws and regulations. Asset allocations are established in a manner consistent with projected plan liabilities, benefit payments and expected rates of return for the various asset classes. The expected rate of return for the investment portfolio is based on expected rates of return for various asset classes, as well as historical asset class and fund performance. The following table sets forth the change in benefit obligation for the pension and postretirement benefit plans as of December 31, 2023: Pension United States of America United Kingdom Mexico Change in benefit obligation: Bargaining Salaried Supplemental Pension Pension Total Postretirement Benefit obligation at the beginning of year $ 474.9 $ 128.1 $ 15.5 $ 47.7 $ 0.4 $ 666.6 $ 87.4 Service cost 9.5 0.9 — — — 10.4 0.7 Interest cost 25.9 6.7 0.9 2.3 — 35.8 4.7 Actuarial (gains) losses 19.1 5.7 0.7 7.3 — 32.8 3.8 Benefits paid ( 38.5 ) ( 11.4 ) ( 0.6 ) ( 3.3 ) — ( 53.8 ) ( 11.7 ) Settlements — ( 6.0 ) — — — ( 6.0 ) — Foreign currency translation adjustment — — — 2.7 0.1 2.8 — Benefit obligation at the end of year $ 490.9 $ 124.0 $ 16.5 $ 56.7 $ 0.5 $ 688.6 $ 84.9 Significant actuarial losses related to changes in benefit obligations for 2023 primarily resulted from a decrease in discount rates. The following table sets forth the change in benefit obligation for the pension and postretirement benefit plans as of December 31, 2022: Pension United States of America United Kingdom Mexico Change in benefit obligation: Bargaining Salaried Supplemental Pension Pension Total Postretirement Benefit obligation at the beginning of year $ 1,025.4 $ 187.4 $ 23.6 $ 82.4 $ 0.4 $ 1,319.2 $ 117.8 Service cost 13.9 0.3 — — — 14.2 1.1 Interest cost 31.1 6.5 0.7 1.3 — 39.6 3.4 Actuarial (gains) losses ( 203.6 ) ( 34.0 ) ( 6.5 ) ( 25.3 ) — ( 269.4 ) ( 24.0 ) Benefits paid ( 51.0 ) ( 11.6 ) ( 0.6 ) ( 2.5 ) — ( 65.7 ) ( 10.9 ) Settlements ( 340.9 ) ( 20.5 ) ( 1.7 ) — — ( 363.1 ) — Foreign currency translation adjustment — — — ( 8.2 ) — ( 8.2 ) — Benefit obligation at the end of year $ 474.9 $ 128.1 $ 15.5 $ 47.7 $ 0.4 $ 666.6 $ 87.4 Significant actuarial gains related to changes in benefit obligations for 2022 primarily resulted from an increase in discount rates. Significant settlements were a result of the Bargaining Plan annuity purchase as well as lump sum payments during 2022. The following table sets forth the change in plan assets and funded status for the pension and postretirement benefit plan as of December 31, 2023: Pension United States of America United Kingdom Mexico Change in plan assets: Bargaining Salaried Supplemental Pension Pension Total Postretirement Fair value of plan assets at the beginning of year $ 353.9 $ 137.7 $ — $ 57.5 $ 0.3 $ 549.4 $ 59.2 Actual return on plan assets 19.3 9.3 — 2.5 — 31.1 5.3 Company contributions / payments — — 0.6 1.2 — 1.8 1.0 Benefits paid ( 38.5 ) ( 11.4 ) ( 0.6 ) ( 3.3 ) — ( 53.8 ) ( 11.7 ) Settlements — ( 6.0 ) — — — ( 6.0 ) — Foreign currency translation adjustment — — — 3.1 — 3.1 — Fair value of plan assets at end of year $ 334.7 $ 129.6 $ — $ 61.0 $ 0.3 $ 525.6 $ 53.8 Funded status at end of year $ ( 156.2 ) $ 5.6 $ ( 16.5 ) $ 4.3 $ ( 0.2 ) $ ( 163.0 ) $ ( 31.1 ) The following table sets forth the change in plan assets and funded status for the pension and postretirement benefit plan as of December 31, 2022: Pension United States of America United Kingdom Mexico Change in plan assets: Bargaining Salaried Supplemental Pension Pension Total Postretirement Fair value of plan assets at the beginning of year $ 862.8 $ 205.7 $ — $ 107.2 $ 0.3 $ 1,176.0 $ 76.8 Actual return on plan assets ( 119.7 ) ( 35.9 ) — ( 38.0 ) — ( 193.6 ) ( 8.8 ) Company contributions / payments — — 2.3 1.3 — 3.6 2.1 Benefits paid ( 51.0 ) ( 11.6 ) ( 0.6 ) ( 2.5 ) — ( 65.7 ) ( 10.9 ) Settlements ( 338.2 ) ( 20.5 ) ( 1.7 ) — — ( 360.4 ) — Foreign currency translation adjustment — — — ( 10.5 ) — ( 10.5 ) — Fair value of plan assets at end of year $ 353.9 $ 137.7 $ — $ 57.5 $ 0.3 $ 549.4 $ 59.2 Funded status at end of year $ ( 121.0 ) $ 9.6 $ ( 15.5 ) $ 9.8 $ ( 0.1 ) $ ( 117.2 ) $ ( 28.2 ) The Bargaining Plan, Salaried Plan, and Supplemental Plan have a provision that permits employees to elect to receive their pension benefits in a lump sum upon retirement. The Company's accounting policy is to recognize settlements during the quarter in which it is projected that the costs of all settlements during the year will be greater than the sum of the service cost and interest cost components. In the first quarter of 2023, in anticipation of receiving the regulatory approval to move forward with the plan termination process, the cumulative costs of all lump sum payments and other settlements were projected to exceed this threshold during 2023 for the Salaried Plan. Ultimately, these costs did not exceed this threshold for the Salaried Plan during 2023. The Salaried Plan's pension obligations and plan assets were remeasured during each quarter of 2023. In the first quarter of 2022, the cumulative cost of all lump sum payments exceeded this threshold for the Supplemental Plan. Additionally, in the first quarter of 2022, the cumulative costs of all lump sum payments were projected to exceed this threshold during 2022 for the Salaried Plan. These costs did ultimately exceed this threshold for the Salaried Plan during the second quarter of 2022. Also, during the second quarter of 2022, the cumulative costs of all lump sum payments were projected to exceed this threshold in 2022 for the Bargaining Plan. These costs did ultimately exceed this threshold for the Bargaining Plan during the third quarter of 2022. These payments constitute a partial settlement, which is a significant event requiring remeasurement of both plan assets and benefit obligations. As a result, the Company completed a full remeasurement of its pension obligations and plan assets associated with the Supplemental Plan during the first quarter of 2022. No further remeasurement was required in 2022 related to the Supplemental Plan, as no further lump sum payments were made. The Salaried Plan's pension obligations and plan assets were remeasured during each quarter of 2022. We also completed a full remeasurement of the Bargaining Plan's pension obligations and plan assets during the second, third, and fourth quarters of 2022. For the years ended December 31, 2023 and 2022 , all pension plans had administrative expenses of $ 2.9 million and $ 5.1 million, respectively. These expenses are included in benefits paid in the tables above. The accumulated benefit obligation at December 31, 2023 exceeded the fair value of plan assets for the Bargaining Plan and the unfunded Supplemental Plan. For the Bargaining Plan and Supplemental Plan, the accumulated benefit obligation was $ 486.1 million and $ 16.6 million, respectively, as of December 31, 2023. The total pension accumulated benefit obligation for all plans was $ 683.7 million and $ 660.6 million as of December 31, 2023 and 2022, respectively. Amounts recognized on the balance sheet at December 31, 2023 for the Company's pension and postretirement benefit plans include: Pension United States of America United Kingdom Mexico Bargaining Salaried Supplemental Pension Pension Total Postretirement Non-current assets $ — $ 5.6 $ — $ 4.3 $ — $ 9.9 $ — Current liabilities ( 41.7 ) — ( 0.6 ) — — ( 42.3 ) ( 1.2 ) Non-current liabilities ( 114.5 ) — ( 15.9 ) — ( 0.2 ) ( 130.6 ) ( 29.9 ) Total $ ( 156.2 ) $ 5.6 $ ( 16.5 ) $ 4.3 $ ( 0.2 ) $ ( 163.0 ) $ ( 31.1 ) Amounts recognized on the balance sheet at December 31, 2022 for the Company's pension and postretirement benefit plans include: Pension United States of America United Kingdom Mexico Bargaining Salaried Supplemental Pension Pension Total Postretirement Non-current assets $ — $ 9.6 $ — $ 9.8 $ — $ 19.4 $ — Current liabilities — — ( 0.6 ) — — ( 0.6 ) ( 1.4 ) Non-current liabilities ( 121.0 ) — ( 15.0 ) — ( 0.1 ) ( 136.1 ) ( 26.8 ) Total $ ( 121.0 ) $ 9.6 $ ( 15.6 ) $ 9.8 $ ( 0.1 ) $ ( 117.3 ) $ ( 28.2 ) Included in accumulated other comprehensive income (loss) at December 31, 2023 were the following before-tax amounts that had not been recognized in net periodic benefit cost: Pension United States of America United Kingdom Mexico Bargaining Salaried Supplemental Pension Pension Total Postretirement Unrecognized prior service (benefit) cost $ 11.1 $ — $ — $ 0.5 $ — $ 11.6 $ ( 44.0 ) Included in accumulated other comprehensive income (loss) at December 31, 2022 were the following before-tax amounts that had not been recognized in net periodic benefit cost: Pension United States of America United Kingdom Mexico Bargaining Salaried Supplemental Pension Pension Total Postretirement Unrecognized prior service (benefit) cost $ 12.4 $ — $ — $ 0.5 $ — $ 12.9 $ ( 49.9 ) The weighted average assumptions used in determining benefit obligation as of December 31, 2023 and 2022 were as follows: Pension Postretirement Assumptions: 2023 2022 2023 2022 Discount rate 5.33 % 5.61 % 5.43 % 5.70 % Future compensation assumption 3.00 % 3.00 % n/a n/a The weighted average assumptions used in determining benefit cost for the years ended December 31, 2023 and 2022 were as follows: Pension Postretirement Assumptions: 2023 2022 2023 2022 Discount rate 5.61 % 2.96 % 5.70 % 3.00 % Future compensation assumption 3.00 % 3.00 % n/a n/a Expected long-term return on plan assets 7.13 % 5.96 % 6.25 % 4.75 % The discount rate assumption is based on current rates of high-quality long-term corporate bonds over the same period that benefit payments will be required to be made. The expected rate of return on plan assets assumption is based on the weighted-average expected return on the various asset classes in the plans’ portfolios. The asset class return is developed using historical asset return performance as well as current market conditions such as inflation, interest rates and equity market performance. For measurement purposes, the weighted-average annual rate of increase in the per capita cost ("health care cost trend rate") was not applicable for the years 2023 and 2022. The components of net periodic benefit cost (income) for the year ended December 31, 2023 were as follows: Pension United States of America United Kingdom Mexico Components of net periodic benefit cost (income): Bargaining Salaried Supplemental Pension Pension Total Postretirement Service cost $ 9.5 $ 0.9 $ — $ — $ — $ 10.4 $ 0.7 Interest cost 25.9 6.7 0.9 2.3 — 35.8 4.7 Expected return on plan assets ( 26.9 ) ( 7.5 ) — ( 2.7 ) — ( 37.1 ) ( 3.4 ) Amortization of prior service cost 1.3 — — — — 1.3 ( 6.0 ) Settlements — — — — — — — Net remeasurement losses (gains) 26.6 4.0 0.6 7.5 — 38.7 1.9 Net Periodic Benefit Cost (Income) $ 36.4 $ 4.1 $ 1.5 $ 7.1 $ — $ 49.1 $ ( 2.1 ) The components of net periodic benefit cost (income) for the year ended December 31, 2022 were as follows: Pension United States of America United Kingdom Mexico Components of net periodic benefit cost (income): Bargaining Salaried Supplemental Pension Pension Total Postretirement Service cost $ 13.9 $ 0.3 $ — $ — $ — $ 14.2 $ 1.1 Interest cost 31.1 6.5 0.7 1.3 — 39.6 3.4 Expected return on plan assets ( 46.7 ) ( 5.0 ) — ( 3.2 ) — ( 54.9 ) ( 3.4 ) Amortization of prior service cost 1.3 — — — — 1.3 ( 6.0 ) Settlements ( 2.7 ) — — — — ( 2.7 ) — Net remeasurement losses (gains) ( 37.2 ) 6.9 ( 6.5 ) 15.9 — ( 20.9 ) ( 11.8 ) Net Periodic Benefit Cost (Income) $ ( 40.3 ) $ 8.7 $ ( 5.8 ) $ 14.0 $ — $ ( 23.4 ) $ ( 16.7 ) The components of net periodic benefit cost (income) for the year ended December 31, 2021 were as follows: Pension United States of America United Kingdom Mexico Components of net periodic benefit cost (income): Bargaining Salaried Supplemental Pension Pension Total Postretirement Service cost $ 17.0 $ 0.4 $ — $ — $ — $ 17.4 $ 1.2 Interest cost 28.4 5.9 0.8 1.1 — 36.2 3.2 Expected return on plan assets ( 51.5 ) ( 12.6 ) — ( 3.3 ) — ( 67.4 ) ( 3.4 ) Amortization of prior service cost 0.2 — — — — 0.2 ( 6.0 ) Curtailment — — — — — — — Net remeasurement losses (gains) ( 15.1 ) 2.5 ( 1.5 ) ( 1.1 ) — ( 15.2 ) ( 4.9 ) Net Periodic Benefit Cost (Income) $ ( 21.0 ) $ ( 3.8 ) $ ( 0.7 ) $ ( 3.3 ) $ — $ ( 28.8 ) $ ( 9.9 ) Metallus recognizes its overall responsibility to ensure that the assets of its various defined benefit pension plans are managed effectively and prudently and in compliance with its policy guidelines and all applicable laws. Preservation of capital is important; however, Metallus also recognizes that appropriate levels of risk are necessary to allow its investment managers to achieve satisfactory long-term results consistent with the objectives and the fiduciary character of the pension funds. Asset allocations are established in a manner consistent with projected plan liabilities, benefit payments and expected rates of return for various asset classes. The expected rate of return for the investment portfolios is based on expected rates of return for various asset classes, as well as historical asset class and fund performance. The target allocations for each plan's assets are as follows: Pension United States of America United Kingdom Mexico Target Allocations: Bargaining Salaried Supplemental Pension Pension Weighted Postretirement Equity securities 38.0 % — n/a 17.5 % — 26.2 % 26.0 % Debt securities 34.0 % 100.0 % n/a 65.0 % 100.0 % 53.9 % 67.0 % Other investments 28.0 % — n/a 17.5 % — 19.9 % 7.0 % Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date ("exit price"). The inputs used to measure fair value are classified into the following hierarchy: Level 1 - Unadjusted quoted prices in active markets for identical assets or liabilities. Level 2 - Unadjusted quoted prices in active markets for similar assets or liabilities, or unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs other than quoted prices that are observable for the asset or liability. Level 3 - Unobservable inputs for the asset or liability. The following table presents the fair value hierarchy for those investments of the Company's pension assets measured at fair value on a recurring basis as of December 31, 2023: Total Level 1 Level 2 Level 3 Assets: Cash and cash equivalents $ 5.8 $ — $ 5.8 $ — U.S government and agency securities 59.8 50.7 9.1 — Corporate bonds 39.8 — 39.8 — Mutual fund - equities 83.3 83.3 — — Mutual fund - fixed income 12.2 12.2 — — Mutual fund - tactical tilt 10.6 10.6 — — Real estate 14.1 — — 14.1 Private debt 25.7 — — 25.7 Other 0.6 — 0.6 — Total Assets in the fair value hierarchy $ 251.9 $ 156.8 $ 55.3 $ 39.8 Assets measured at net asset value (1) 273.7 — — — Total Assets $ 525.6 $ 156.8 $ 55.3 $ 39.8 (1) Certain assets that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. Such assets include common collective trusts that invest in equity securities and fixed income securities, limited partnerships, real estate partnerships, and hedge funds. As of December 31, 2023 , these assets are redeemable at net asset value within 90 days, except for certain private investments with an estimated liquidation period of one to ten years. The following table presents the fair value hierarchy for those investments of the Company's pension assets measured at fair value on a recurring basis as of December 31, 2022: Total Level 1 Level 2 Level 3 Assets: Cash and cash equivalents $ 58.4 $ 3.0 $ 55.4 $ — U.S government and agency securities 53.7 49.4 4.3 — Corporate bonds 113.0 — 113.0 — Equity securities 14.5 14.5 — — Real estate 7.6 — — 7.6 Private debt 18.8 — — 18.8 Total Assets in the fair value hierarchy $ 266.0 $ 66.9 $ 172.7 $ 26.4 Assets measured at net asset value (1) 283.4 — — — Total Assets $ 549.4 $ 66.9 $ 172.7 $ 26.4 (1) Certain assets that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. Such assets include common collective trusts that invest in equity securities and fixed income securities, limited partnerships, real estate partnerships, and hedge funds. As of December 31, 2022 , these assets were redeemable at net asset value within 90 days. The following table sets forth a summary of changes in the fair value of the Company's pension plan level three assets for the year ended December 31, 2023: Level 3 assets only 2023 Balance at the beginning of year $ 26.4 Transfers in and/or out of Level 3 — Actual return on plan assets: Realized gain (loss) ( 0.6 ) Net unrealized gain (loss) 2.1 Purchases, sales, issuances and settlements: Purchases 14.3 Sales ( 2.4 ) Balance at the end of year $ 39.8 The following table presents the fair value hierarchy for those investments of the Company's postretirement assets measured at fair value on a recurring basis as of December 31, 2023: Total Level 1 Level 2 Level 3 Assets: Cash and cash equivalents $ 2.2 $ 2.2 $ — $ — Mutual fund - equities 13.5 13.5 — — Mutual fund - fixed income 7.3 7.3 — — Mutual fund - real assets 1.1 1.1 — — Mutual fund - tactical tilt 2.5 2.5 — — Total Assets in the fair value hierarchy $ 26.6 $ 26.6 $ — $ — Assets measured at net asset value (1) 27.2 — — — Total Assets $ 53.8 $ 26.6 $ — $ — (1) Certain assets that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. Such assets include common collective trusts that invest in equity securities and fixed income securities. As of December 31, 2023, these assets are redeemable at net asset value on a daily basis. The following table presents the fair value hierarchy for those investments of the Company's postretirement assets measured at fair value on a recurring basis as of December 31, 2022: Total Level 1 Level 2 Level 3 Assets: Cash and cash equivalents $ 1.4 $ 1.4 $ — $ — Mutual fund - fixed income 4.7 4.7 — — Total Assets in the fair value hierarchy $ 6.1 $ 6.1 $ — $ — Assets measured at net asset value (1) 53.1 — — — Total Assets $ 59.2 $ 6.1 $ — $ — (1) Certain assets that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. Such assets include common collective trusts that invest in equity securities, fixed income securities, and limited partnerships. As of December 31, 2022 , these assets were redeemable at net asset value within 90 days. Future benefit payments are expected to be as follows: Pension United States of America United Kingdom Mexico Benefit Payments: Bargaining Salaried (1) Supplemental Pension Pension Total Postretirement 2024 39.4 30.3 0.6 2.8 — 73.1 9.7 2025 40.3 10.5 0.6 2.8 — 54.2 8.9 2026 43.1 10.1 0.5 2.7 — 56.4 8.3 2027 47.2 9.8 13.8 3.1 — 73.9 7.9 2028 46.7 9.5 0.5 3.2 — 59.9 7.5 2029-2033 206.9 41.4 2.0 18.6 — 268.9 33.1 The Company expects to make required contributions and payments to its pension and postretirement plans of $ 45.5 million in the next 12 months and $ 177.0 million from 2025 through 2033. The timing and amount of future required pension contributions is significantly affected by asset returns and actuarial assumptions. (1) As part of the termination of the Salaried Plan, an irrevocable annuity contract is expected to be purchased from an insurance company in 2024. Shortly thereafter, the responsibility for all future Salaried Plan benefit payments will be assumed by the selected insurance company. Defined Contribution Plans The Company recorded expense primarily related to employer matching and non-discretionary contributions to these defined contribution plans of $ 3.4 million in 2023 , $ 3.3 million in 2022 , and $ 2.8 million in 2021 .

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	Note 16 - Stock-Based Compensation Description of the Plan On May 6, 2020, the Company's shareholders approved the 2020 Equity and Incentive Compensation Plan ("2020 Plan"), which replaced the previously approved Amended and Restated 2014 Equity and Incentive Compensation Plan ("2014 Plan"). The 2020 Plan authorizes the Compensation Committee to provide cash awards and equity-based compensation in the form of stock options, stock appreciation rights, restricted shares, restricted share units, performance shares, performance units, dividend equivalents, and certain other awards for the primary purpose of providing our employees, officers and directors incentives and rewards for service and/or performance. Subject to adjustment as described in the 2020 Plan, and subject to the 2020 Plan share counting rules, a total of 2.0 million common shares of the Company are available for awards granted under the 2020 Plan (plus shares subject to awards granted under the 2020 Plan or the 2014 Plan that are canceled or forfeited, expire, are settled for cash, or are unearned to the extent of such cancellation, forfeiture, expiration, cash settlement or unearned amount, as further described in the 2020 Plan). These shares may be shares of original issuance or treasury shares, or a combination of both. The aggregate number of shares available under the 2020 Plan will generally be reduced by one common share for every one share subject to an award granted under the 2020 Plan. The 2020 Plan also provides that, subject to adjustment as described in the 2020 Plan: (1) the aggregate number of common shares actually issued or transferred upon the exercise of incentive stock options will not exceed 2.0 million common shares; and (2) no non-employee director of the Company will be granted, in any period of one calendar year, compensation for such service having an aggregate maximum value (measured at the grant date as applicable, and calculating the value of any awards based on the grant date fair value for financial reporting purposes) in excess of $ 0.5 million. On May 5, 2021, shareholders approved the Amended and Restated 2020 Equity and Incentive Compensation Plan (the “Amended 2020 Plan”), which amended and restated the 2020 plan. In general, the Amended 2020 Plan modified the 2020 Plan to (1) increase the number of common shares, without par value, of the Company available for awards by 2,000,000 shares, (2) correspondingly increase the limit on shares that may be issued or transferred upon the exercise of incentive stock options by 2,000,000 shares, (3) remove the 2020 Plan’s full value award limit of 1.8 million shares and (4) extend the plan term until May 5, 2031 . In addition, the Amended 2020 Plan made certain other conforming, clarifying or non-substantive changes to the terms of the 2020 Plan to implement the Amended 2020 Plan but did not make other material changes to the 2020 Plan. Stock Options There were no stock options granted during the years ended December 31, 2023, 2022 and 2021. The following summarizes the Company's stock option activity from January 1, 2023 to December 31, 2023: Number of Weighted Weighted Aggregate Outstanding as of December 31, 2022 1,119,523 $ 18.85 Granted — — — — Exercised ( 291,928 ) 10.11 — — Canceled, forfeited or expired ( 206,245 ) 33.93 — — Outstanding as of December 31, 2023 621,350 $ 17.95 3.5 $ 5.6 Options expected to vest 66,360 5.26 6.2 1.2 Options exercisable 554,990 $ 19.47 3.1 $ 4.4 Time-Based Restricted Stock Units Time-based restricted stock units are issued with the fair value equal to the closing market price of Metallus common shares on the date of grant. These restricted stock units do not have any performance conditions for vesting. Expense is recognized over the service period, adjusted for any forfeitures that occur during the vesting period. The following summarizes the Company's stock-settled, time-based restricted stock unit activity from January 1, 2023 to December 31, 2023: Number of Weighted Outstanding as of December 31, 2022 1,546,002 $ 9.29 Granted 385,959 18.52 Vested ( 302,935 ) 11.41 Canceled, forfeited or expired ( 9,307 ) 18.19 Outstanding as of December 31, 2023 1,619,719 $ 11.99 Performance-Based Restricted Stock Units Annual grants of performance-based restricted stock units are generally earned (determined under a Compensation Committee approved matrix) based on the Company's relative total shareholder return as compared to an identified peer group of steel companies. The overall vesting period is generally three years, with relative total shareholder return measured for the one, two and three-year periods creating effectively a “nested” 1-year, 2-year, and 3-year performance period. Relative total shareholder return is calculated for each nested performance period by taking the beginning and ending price points based off a 20 -trading day average closing stock price as of December 31. The following summarizes the Company's stock-settled performance-based restricted stock unit activity from January 1, 2023 to December 31, 2023: Number of Weighted Outstanding as of December 31, 2022 968,415 $ 10.21 Granted 211,639 23.13 Vested ( 167,694 ) 4.98 Canceled, forfeited or expired 2,298 23.44 Outstanding as of December 31, 2023 1,014,658 $ 13.76 Transformation Incentive Grant Program On December 15, 2023, the Board of approved and authorized a performance-based Transformation Incentive Grant program (the “Transformation Incentive Grant Program”). Under the Transformation Incentive Grant Program, effective December 15, 2023, certain employees of the Company were granted performance-based Restricted Share Unit awards designed to be earned from 0 percent to 200 percent of target levels depending on the degree to which the closing price performance of the Company's common shares satisfies specific average per share closing price goals (achieved if the goal price is met or exceeded by the 20 -trading-day average closing price for each trading day in any 20 -consecutive-day trading period) during a performance period running from December 1, 2023 through December 31, 2026. Any performance shares earned will pay out in two equal installments in early 2027 and 2028, generally conditioned on continued employment with the Company until the applicable vesting date. Different payout curves apply for each participant group (Tier 1-2 or Tier 3-4). The following summarizes the Company's Transformation Incentive Grant Program activity from January 1, 2023 to December 31, 2023: Number of Weighted Outstanding as of December 31, 2022 — $ — Granted (Tier 1-2) 200,000 22.22 Granted (Tier 3-4) 150,000 22.78 Canceled, forfeited or expired — — Outstanding as of December 31, 2023 350,000 $ 22.46 Other Information Metallus recognized stock-based compensation expense of $ 11.5 million, $ 8.8 million and $ 7.3 million for the years ended December 31, 2023, 2022 and 2021, respectively. As of December 31, 2023 , future stock-based compensation expense related to the unvested portion of all awards is approximately $ 19.9 million, which is expected to be recognized over a weighted average period of 2.4 year s.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2023
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	Note 17 - Accumulated Other Comprehensive Income (Loss) Changes in accumulated other comprehensive income (loss) for the years ended December 31, 2023 and 2022 by component were as follows: Foreign Currency Pension and Total Balance as of December 31, 2022 $ ( 6.8 ) $ 21.5 $ 14.7 Other comprehensive income before reclassifications, before income tax — — — Amounts reclassified from accumulated other comprehensive income 0.3 ( 4.9 ) ( 4.6 ) Amounts deferred to accumulated other comprehensive income — 2.3 2.3 Tax effect — — — Net current period other comprehensive income (loss), net of income taxes 0.3 ( 2.6 ) ( 2.3 ) Balance as of December 31, 2023 $ ( 6.5 ) $ 18.9 $ 12.4 Foreign Currency Pension and Total Balance as of December 31, 2021 $ ( 5.1 ) $ 25.8 $ 20.7 Other comprehensive income before reclassifications, before income tax ( 1.7 ) — ( 1.7 ) Amounts reclassified from accumulated other comprehensive income — ( 4.7 ) ( 4.7 ) Amounts deferred to accumulated other comprehensive income — — — Tax effect — 0.4 0.4 Net current period other comprehensive income (loss), net of income taxes ( 1.7 ) ( 4.3 ) ( 6.0 ) Balance as of December 31, 2022 $ ( 6.8 ) $ 21.5 $ 14.7 The amount reclassified from accumulated other comprehensive income (loss) for the years ended December 31, 2023 and December 31, 2022 for the pension and postretirement liability adjustment was included in other (income) expense, net in the Consolidated Statements of Operations. The amount deferred to accumulated other comprehensive income (loss) for the year ended December 31, 2021 was a result of a plan amendment to the Company's Bargaining Plan. For more details refer to "Note 15 - Retirement and Postretirement Plans."

Contingencies

Contingencies	12 Months Ended
	Dec. 31, 2023
Loss Contingency Accrual, Disclosures [Abstract]
Contingencies	Note 18 – Contingencies Metallus has a number of loss exposures incurred in the ordinary course of business, such as environmental claims, product warranty claims, employee-related matters, and other litigation. Establishing loss reserves for these matters requires management’s estimate and judgment regarding risk exposure and ultimate liability or realization. These loss reserves are reviewed periodically and adjustments are made to reflect the most recent facts and circumstances. Accruals related to environmental claims represent management’s best estimate of the fees and costs associated with these claims. Although it is not possible to predict with certainty the outcome of such claims, management believes that their ultimate dispositions should not have a material adverse effect on our financial position, cash flows or results of operations. At both December 31, 2023 and 2022, Metallus had a $ 1.1 million contingency reserve related to loss exposures incurred in the ordinary course of business.

Subsequent Event

Subsequent Event	12 Months Ended
	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Event	Note 19 – Subsequent Event On February 27, 2024, the Company entered an agreement with the United States Army. The agreement provides for up to $ 99 million in funding from the Army, half of which is currently committed with the balance subject to mutual agreement as the final project details are presented to the Army. This funding will support new assets aimed at bolstering the Army's mission of ramping up artillery shell production in the coming years. The Company is targeting late 2025 for the new assets to be operational with funding to be provided throughout the procurement and installation process.

Schedule II-Valuation and Quali

Schedule II-Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2023
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule II-Valuation and Qualifying Accounts	Schedule II-Valuation and Qualifying Accounts Allowance for uncollectible accounts: 2023 2022 2021 Balance at Beginning of Period $ 1.0 $ 1.9 $ 1.3 Additions: Charged to Costs and Expenses (1) 1.2 — 0.6 Deductions (2) ( 0.2 ) ( 0.9 ) — Balance at End of Period $ 2.0 $ 1.0 $ 1.9 Allowance for inventory reserves: 2023 2022 2021 Balance at Beginning of Period $ 0.5 $ 0.8 $ 13.9 Additions: Charged to Costs and Expenses (3) 1.1 0.5 2.8 Deductions (4) ( 0.9 ) ( 0.8 ) ( 15.9 ) Balance at End of Period $ 0.7 $ 0.5 $ 0.8 Valuation allowance on deferred tax assets: 2023 2022 2021 Balance at Beginning of Period $ 13.0 $ 15.5 $ 47.7 Additions: Charged to Costs and Expenses (5) 2.5 — — Charged to Other Accounts (6) — — 4.8 Deductions (7) — ( 2.5 ) ( 37.0 ) Balance at End of Period $ 15.5 $ 13.0 $ 15.5 Provision for uncollectible accounts included in expenses. Actual accounts written off against the allowance, net of recoveries. Provisions for surplus and obsolete inventory and lower cost or net realizable value included in expenses. Inventory items released against the allowance, either via write-off or a recovery. The allowance for inventory reserves decreased in 2021 due to sales of TMS inventory, along with the selling and scrapping of aged inventory. (5) Increase in valuation allowance is recorded as a component of the provision for income taxes. (6) Amount relates to valuation allowances recorded against other comprehensive income (loss). (7) For the year ended December 31, 2022, this amount related to the release of a portion of the U.S. valuation allowance. For the year ended December 31, 2021, this amount relates to the release of the valuation allowance against tax loss carryforwards used during 2021.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Revenue Recognition	Revenue Recognition: Metallus recognizes revenue from contracts at a point in time when it has satisfied its performance obligation and the customer obtains control of the goods, at the amount that reflects the consideration the Company expects to receive for those goods. Substantially all performance obligations arise from the sale of manufactured steel products. The Company receives and acknowledges purchase orders from its customers, which define the quantity, pricing, payment and other applicable terms and conditions. In some cases, the Company receives a blanket purchase order from its customer, which includes pricing, payment and other terms and conditions, with quantities defined at the time the customer issues periodic releases from the blanket purchase order. Transfer of control and revenue recognition for substantially all the Company’s sales occur upon shipment or delivery of the product, which is when title, ownership, and risk of loss pass to the customer and is based on the applicable customer shipping terms. The Company invoices its customers at the time of title transfer. Payment terms are generally 30 days from the invoice date. Invoiced amounts are usually inclusive of shipping and handling activities incurred. Shipping and handling activities billed are included in net sales in the Consolidated Statements of Operations. The related costs incurred by the Company for the delivery of goods are classified as cost of products sold in the Consolidated Statements of Operations. Certain contracts contain variable consideration, which primarily consists of rebates that are accounted for in net sales and accrued based on the estimated probability of the requirements being met. Sales returns and allowances are treated as a reduction to net sales and are provided for primarily based on historical experience. These reserves also capture any potential warranty claims, which normally result in returned or replaced product. The Company’s contracts with certain Manufactured Components customers extend multiple years and generally average five years. While these contracts set the duration of time, they do not cover or guarantee volumes but rather are focused on piece prices, which are established at the inception of the contract. From time to time, subsequent pricing adjustments are agreed to through negotiation. Pricing adjustments are occasionally determined retroactively based on historical shipments. The Company recognizes revenue for these subsequent price adjustments when they are determined to be probable and estimable. For the year ended December 31, 2023, the Company recognized $ 16.0 million in subsequent pricing adjustments.
Cash Equivalents and Restricted Cash	Cash Equivalents and Restricted Cash: Metallus considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. The Company's restricted cash balance represents an imprest cash account used for the funding of employee healthcare costs. Funding of this account began during the first quarter of 2022 when the Company changed its healthcare plan administrator. The balance of restricted cash as of December 31, 2023 was $ 0.7 million, which is included in other current assets on the Consolidated Balance Sheets. The Company had $ 0.6 million of restricted cash as of December 31, 2022 .
Accounts Receivables, Net	Accounts Receivables, Net: The Company’s accounts receivables arise from sales to customers across the industrial, automotive, aerospace & defense, and energy end markets. The allowance for doubtful account reserve has been established using qualitative and quantitative methods. In general, account balances are fully reserved when greater than one year of age or sent to third party collection. Account balances for customers that are viewed as higher risk are also analyzed for a reserve. In addition to these methods, the allowance for doubtful accounts is adjusted for forward-looking estimates of uncollectible balances based on end-market outlook and dynamics. Historically, write-offs for Metallus' allowance for doubtful accounts have been immaterial.
Inventories, Net	Inventories, Net: Inventories are stated at lower of cost or net realizable value. All inventories, including raw materials, manufacturing supplies inventory, as well as international (outside the U.S.) inventories, have been valued using the FIFO or average cost method.
Property, Plant and Equipment, Net	Property, Plant and Equipment, Net: Property, plant and equipment, net are valued at cost less accumulated depreciation. Maintenance and repairs are charged to expense as incurred. The provision for depreciation is computed principally by the straight-line method based upon the estimated useful lives of the assets. The useful lives are approximately 30 years for buildings and 3 to 20 years for machinery and equipment.
Impairment and Disposal of Long-lived Assets, Net	Impairment and Disposal of Long-lived Assets, Net: Long-lived assets (including property, plant and equipment, tangible assets and intangible assets subject to amortization) are reviewed for impairment when events or changes in circumstances have occurred indicating that the carrying value of the assets may not be recoverable. Metallus tests recoverability of long-lived assets at the lowest level for which there are identifiable cash flows that are independent from the cash flows of other assets. Assets and asset groups held and used are measured for recoverability by comparing the carrying amount of the asset or asset group to the sum of future undiscounted net cash flows expected to be generated by the asset or asset group. If an asset or asset group is considered to be impaired, the impairment loss that would be recognized is the amount by which the carrying amount of the assets exceeds the fair value of the assets. To determine fair value, Metallus uses internal cash flow estimates discounted at an appropriate interest rate, third party appraisals, as appropriate, and/or market prices of similar assets, when available. Refer to “Note 6 - Disposition of Non-Core Assets” and “Note 11 - Property, Plant and Equipment” for additional information.
Income Taxes	Income Taxes: Deferred tax assets and liabilities are recorded for the future tax consequences attributable to differences between financial statement carrying amounts of existing assets and liabilities and their respective tax bases, as well as net operating loss and tax credit carryforwards. Metallus accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. Metallus recognizes deferred tax assets to the extent Metallus believes these assets are more likely than not to be realized. In making such a determination, Metallus considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If Metallus determines that it would be able to realize deferred tax assets in the future in excess of their net recorded amount, Metallus would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. Metallus records uncertain tax positions in accordance with applicable accounting guidance, on the basis of a two-step process whereby (1) Metallus determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position, and (2) for those tax positions that meet the more-likely-than-not recognition threshold, Metallus recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. Metallus recognizes interest and penalties related to unrecognized tax benefits within the provision (benefit) for income taxes line in the accompanying Consolidated Statements of Operations, if applicable. Accrued interest and penalties are included within the related tax liability line in the Consolidated Balance Sheets.
Pension and Other Postretirement Benefits	Pension and Other Postretirement Benefits: Metallus recogn izes an overfunded status or underfunded status (e.g., the difference between the fair value of plan assets and the benefit obligations) as either an asset or a liability for its defined benefit pension and other postretirement benefit plans on the Consolidated Balance Sheets. The Company recognizes actuarial gains and losses immediately through net periodic benefit cost in the Consolidated Statements of Operations upon the annual remeasurement at December 31, or on an interim basis as triggering events warrant remeasurement. An example of a potential triggering event would be settlements. The Company’s accounting policy is to recognize settlements during the quarter in which it is projected that the costs of all settlements during the year will be greater than the sum of the service cost and interest cost components of net periodic benefit cost. In addition, the Company uses fair value to account for the value of plan assets.
Stock-Based Compensation	Stock-Based Compensation: Metallus recognizes stock-based compensation expense based on the grant date fair value of the stock-based awards over their required vesting period on a straight-line basis, whether the awards were granted with graded or cliff vesting. Stock options are issued with an exercise price equal to the closing market price of Metallus common shares on the date of grant. The fair value of stock options is determined using a Black-Scholes option pricing model, which incorporates assumptions regarding the expected volatility, the expected option life, the risk-free interest rate and the expected dividend yield. Annual grants of performance-based restricted stock units vest based on achievement of a relative total shareholder return ("TSR") metric. The TSR metric is considered a market condition, which requires Metallus to reflect it in the fair value on grant date using an advanced option-pricing model. The fair value of each performance share was therefore determined using a Monte Carlo valuation model, a generally accepted lattice pricing model. The Monte Carlo valuation model, among other factors, uses commonly-accepted economic theory underlying all valuation models, estimates fair value using simulations of future share prices based on stock price behavior and considers the correlation of peer company returns in determining fair value. In the fourth quarter, the Board approved and authorized a performance-based Transformation Incentive Grant program (the “Transformation Incentive Grant Progra m”). Under the Transformation Incentive Grant Program, certain employees were granted performance-based Restricted Share Unit awards designed to be earned from 0 percent to 200 percent of target levels depending on the degree to which the closing price performance of the Company's common shares satisfies specific average per share closing price goals during a performance period running from December 1, 2023 through December 31, 2026. Shares earned, if any, will then pay out in two equal installments in early 2027 and 2028, generally conditioned on continued employment with the Company until the applicable vesting date. Similar to the annual performance-based restricted stock units, the fair value of each share is determined using a Monte Carlo valuation model, a generally accepted lattice pricing model. The fair value of stock-based awards that will settle in Metallus common shares, other than stock options and performance-based restricted stock units, is based on the closing market price of Metallus common shares on the grant date. Metallus recognizes all excess tax benefits and tax deficiencies as income tax expense or benefit in the Consolidated Statements of Operations. The excess tax benefits and tax deficiencies are considered discrete items in the reporting period they occur and are not included in the estimate of an entity’s annual effective tax rate.
Adoption of New Accounting Standards	Adoption of New Accounting Standards The Company did not adopt any Accounting Standard Updates (“ASU”) during 2023. Accounting Standards Issued But Not Yet Adopted The Company has considered the recent ASU's issued by the Financial Accounting Standards Board summarized below: Standard Adopted Description Effective Date Impact ASU 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures The standard enhances income tax disclosures primarily related to the rate reconciliation and income taxes paid. Annual periods beginning after December 15, 2024 The Company is currently evaluating the impact of the adoption of this ASU on its results of operations and financial condition. ASU 2023-07, Segment Reporting - Improvements to Reportable Segment Disclosures The standard enhances reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. Annual periods beginning after December 15, 2023, and interim periods beginning after December 15, 2024 The Company is currently evaluating the impact of the adoption of this ASU on its results of operations and financial condition.

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2023
Segment Reporting [Abstract]
Revenue from External Customers by Geographic Areas	Net sales by geographic area are reported by the country in which the customer is domiciled. Year Ended December 31, 2023 2022 2021 Net Sales: United States $ 1,239.4 $ 1,201.3 $ 1,166.1 Foreign 123.0 128.6 116.8 $ 1,362.4 $ 1,329.9 $ 1,282.9
Long-lived Assets by Geographic Areas	Long-lived assets include property, plant and equipment and intangible assets subject to amortization. Long-lived assets by geographic area are reported by the location of the Metallus operations to which the asset is attributed. December 31, 2023 2022 Long-lived Assets, net: United States $ 506.2 $ 503.0 Foreign 0.4 0.6 $ 506.6 $ 503.6

Revenue Recognition (Tables)

Revenue Recognition (Tables)	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table provides the major sources of revenue by end-market for the years ended December 31, 2023, 2022 and 2021: Year Ended December 31, 2023 2022 2021 Industrial $ 533.3 549.0 601.0 Automotive 531.9 539.1 527.9 Aerospace & Defense (1) 115.0 79.7 60.2 Energy 160.4 136.6 62.9 Other (2) 21.8 25.5 30.9 Total Net Sales $ 1,362.4 $ 1,329.9 $ 1,282.9 (1) “Aerospace & Defense” sales by end-market were previously included in "Industrial." (2) “Other” sales by end-market includes the Company’s scrap sales. The following table provides the major sources of revenue by product type for the years ended December 31, 2023, 2022 and 2021: Year Ended December 31, 2023 2022 2021 Bar $ 917.1 $ 887.4 $ 863.6 Tube 170.1 173.7 164.4 Manufactured components 253.4 243.3 224.0 Other (3) 21.8 25.5 30.9 Total Net Sales $ 1,362.4 $ 1,329.9 $ 1,282.9 (3) “Other” for sales by product type relates to the Company’s scrap sales.

Restructuring Charges (Tables)

Restructuring Charges (Tables)	12 Months Ended
	Dec. 31, 2023
Restructuring and Related Activities [Abstract]
Schedule of Restructuring Reserve	The following is a summary of the restructuring reserve for the twelve months ended December 31, 2023 and 2022: Balance at December 31, 2021 $ 4.7 Expenses 0.8 Payments ( 5.0 ) Balance at December 31, 2022 $ 0.5 Expenses — Payments ( 0.5 ) Balance at December 31, 2023 —

Other (Income) Expense, net (Ta

Other (Income) Expense, net (Tables)	12 Months Ended
	Dec. 31, 2023
Other Income and Expenses [Abstract]
Schedule of Other (Income) Expense, Net	The following table provides the components of other (income) expense, net for the years ended December 31, 2023, 2022 and 2021: Year Ended December 31, 2023 2022 2021 Pension and postretirement non-service benefit (income) loss $ ( 4.6 ) $ ( 20.3 ) $ ( 37.2 ) Loss (gain) from remeasurement of benefit plans 40.6 ( 35.4 ) ( 20.1 ) Foreign currency exchange loss (gain) — ( 0.2 ) 0.1 Insurance recoveries ( 31.3 ) ( 34.5 ) — Sales and use tax refund ( 1.4 ) — ( 2.5 ) Miscellaneous (income) expense 0.4 ( 0.2 ) 0.2 Total other (income) expense, net $ 3.7 $ ( 90.6 ) $ ( 59.5 )

Income Tax Provision (Tables)

Income Tax Provision (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign	Income (loss) from operations before income taxes, based on geographic location of the operations to which such earnings are attributable, is provided below. Years Ended December 31, 2023 2022 2021 United States $ 103.2 $ 108.5 $ 171.2 Non-United States ( 6.8 ) ( 11.4 ) 5.5 Income (loss) from operations before income taxes $ 96.4 $ 97.1 $ 176.7
Schedule of (Benefit) Provision for Income Taxes	The provision (benefit) for income taxes consisted of the following: Years Ended December 31, 2023 2022 2021 Current: Federal $ 30.4 $ 0.6 $ 0.2 State and local 6.1 5.7 3.7 Foreign 0.2 0.8 0.6 Total current tax expense (benefit) $ 36.7 $ 7.1 $ 4.5 Deferred: Federal $ ( 9.2 ) $ 24.2 $ 0.8 State and local ( 0.5 ) 0.7 0.3 Foreign — — 0.1 Total deferred tax expense (benefit) ( 9.7 ) 24.9 1.2 Provision (benefit) for incomes taxes $ 27.0 $ 32.0 $ 5.7
Schedule of Effective Income Tax Rate Reconciliation	The reconciliation between Metallus' effective tax rate on income (loss) from continuing operations and the statutory tax rate is as follows: Years Ended December 31, 2023 2022 2021 U.S. federal income tax provision (benefit) at statutory rate $ 20.2 $ 20.4 $ 37.1 Adjustments: State and local income taxes, net of federal tax benefit 4.2 8.4 4.1 Permanent differences 1.2 8.9 ( 0.2 ) Foreign earnings taxed at different rates — ( 3.6 ) ( 0.5 ) Valuation allowance 1.8 ( 2.5 ) ( 34.8 ) U.S. research tax credit ( 0.3 ) ( 0.6 ) — Other items, net ( 0.1 ) 1.0 — Provision (benefit) for income taxes $ 27.0 $ 32.0 $ 5.7 Effective tax rate 28.0 % 32.9 % 3.2 %
Schedule of Deferred Tax Assets and Liabilities	The effect of temporary differences giving rise to deferred tax assets and liabilities at December 31, 2023 and 2022 was as follows: Years Ended December 31, 2023 2022 Deferred tax liabilities: Depreciation $ ( 75.0 ) $ ( 81.4 ) Inventory — — Prepaid insurance ( 1.9 ) — Leases - right-of-use asset ( 2.8 ) ( 3.1 ) Deferred tax liabilities $ ( 79.7 ) $ ( 84.5 ) Deferred tax assets: Tax loss carryforwards $ 16.0 $ 20.5 Pension and postretirement benefits 46.8 35.5 Other employee benefit accruals 8.0 6.6 Lease liability 2.8 3.1 State decoupling 1.2 0.8 Accrued restructuring — 0.1 Capital loss carryforward 0.8 0.8 Intangible assets 0.1 0.2 Inventory 0.8 0.7 Allowance for doubtful accounts 0.5 0.3 Accrued legal — 2.0 Capitalized R&D 3.2 0.9 Other, net — 0.1 Deferred tax assets subtotal $ 80.2 $ 71.6 Valuation allowances ( 15.5 ) ( 13.0 ) Deferred tax assets 64.7 58.6 Net deferred tax assets (liabilities) $ ( 15.0 ) $ ( 25.9 )

Earnings (Loss) Per Share (Tabl

Earnings (Loss) Per Share (Tables)	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the reconciliation of the numerator and the denominator of basic and diluted earnings (loss) per share for the years ended December 31, 2023, 2022 and 2021: Year Ended December 31, 2023 2022 2021 Numerator: Net income (loss), basic $ 69.4 $ 65.1 $ 171.0 Add convertible notes interest 1.0 1.9 4.1 Net income (loss), diluted $ 70.4 $ 67.0 $ 175.1 Denominator: Weighted average shares outstanding, basic 43.8 45.8 45.9 Dilutive effect of equity-based awards 2.1 2.1 1.7 Dilutive effect of convertible notes 1.9 3.6 7.4 Weighted average shares outstanding, diluted 47.8 51.5 55.0 Basic earnings (loss) per share $ 1.58 $ 1.42 $ 3.73 Diluted earnings (loss) per share $ 1.47 $ 1.30 $ 3.18

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2023
Inventory Disclosure [Abstract]
Schedule of Components of Inventory	The components of inventories as of December 31, 2023 and 2022 were as follows: December 31, 2023 2022 Manufacturing supplies $ 51.5 $ 36.9 Raw materials 17.5 23.9 Work in process 109.6 94.7 Finished products 50.1 37.4 Gross inventory 228.7 192.9 Allowance for inventory reserves ( 0.7 ) ( 0.5 ) Total inventories, net $ 228.0 $ 192.4

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment	The components of property, plant and equipment, net as of December 31, 2023 and 2022 were as follows: December 31, 2023 2022 Land $ 11.2 $ 11.2 Buildings and improvements 429.2 414.6 Machinery and equipment 1,367.6 1,391.5 Construction in progress 59.3 30.8 Subtotal 1,867.3 1,848.1 Less allowances for depreciation ( 1,374.8 ) ( 1,362.0 ) Property, plant and equipment, net $ 492.5 $ 486.1
Schedule of Supplemental Cash Flow Information Related to Non-Cash Investing Activity	Supplemental cash flow information related to non-cash investing activity was as follows: Year Ended December 31, 2023 2022 2021 Accrued property, plant and equipment purchases $ 12.1 $ 10.6 $ 3.6

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets	The components of intangible assets, net as of December 31, 2023 and 2022 were as follows: December 31, 2023 December 31, 2022 Gross Accumulated Net Gross Accumulated Net Customer relationships $ 6.3 $ 6.3 $ — $ 6.3 $ 6.2 $ 0.1 Technology use 9.0 9.0 — 9.0 9.0 — Capitalized software 55.6 53.2 2.4 57.9 53.0 4.9 Total intangible assets $ 70.9 $ 68.5 $ 2.4 $ 73.2 $ 68.2 $ 5.0
Schedule of Estimated Annual Amortization Expense	Based upon the intangible assets subject to amortization as of December 31, 2023, Metallus' estimated annual amortization for the five succeeding years is shown below (in millions): Year Amortization 2024 $ 1.3 2025 0.3 2026 0.2 2027 0.1 2028 0.1

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Lease, Cost	The Company recorded lease cost for the years ended December 31, 2023, 2022 and 2021 as follows: Year Ended December 31, 2023 2022 2021 Operating lease cost $ 7.3 $ 6.7 $ 8.2 Short-term lease cost 0.8 0.9 0.7 Total lease cost $ 8.1 $ 7.6 $ 8.9 Supplemental cash flow information related to leases was as follows: Year Ended December 31, 2023 2022 2021 Cash paid for amounts included in the measurement of operating lease liabilities $ 7.1 $ 6.7 $ 8.2 Right-of-use assets obtained in exchange for operating lease obligations $ 5.6 $ 4.5 $ 3.1
Future Lease Maturity	Future minimum lease payments under non-cancellable leases as of December 31, 2023 were as follows: 2024 $ 5.5 2025 3.2 2026 1.7 2027 1.3 After 2028 0.8 Total future minimum lease payments 12.5 Less amount of lease payment representing interest ( 1.1 ) Total present value of lease payments $ 11.4

Financing Arrangements (Tables)

Financing Arrangements (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Instrument [Line Items]
Summary of Current and Non-current Debt	The following table summarizes the current and non-current debt as of December 31, 2023 and 2022: December 31, 2023 2022 Credit Agreement $ — $ — Convertible Senior Notes due 2025 13.2 20.4 Total debt $ 13.2 $ 20.4 Less current portion of debt 13.2 20.4 Total non-current portion of debt $ — $ —
Schedule of Interest (income) Expense	The following table provides the components of interest (income) expense, net for the years ended December 31, 2023, 2022 and 2021: Year Ended December 31, 2023 2022 2021 Interest expense $ 2.7 $ 3.9 $ 6.2 Interest income ( 9.8 ) ( 3.3 ) ( 0.3 ) Interest (income) expense, net $ ( 7.1 ) $ 0.6 $ 5.9
Convertible Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Schedule of Components of Convertible Notes	The components of the Convertible Senior Notes due 2025 as of December 31, 2023 and 2022 were as follows: December 31, 2023 2022 Principal $ 13.3 $ 20.8 Less: Debt issuance costs, net of amortization ( 0.1 ) ( 0.4 ) Less: Debt discount, net of amortization — — Convertible Senior Notes due 2025, net $ 13.2 $ 20.4
Convertible Notes
Debt Instrument [Line Items]
Schedule of Interest (income) Expense	The following table sets forth total interest expense recognized specifically related to the Convertible Notes: Year Ended December 31, 2023 2022 2021 Contractual interest expense $ 0.9 $ 1.7 $ 3.7 Amortization of debt issuance costs 0.1 0.1 0.4 Total $ 1.0 $ 1.8 $ 4.1

Retirement and Postretirement_2

Retirement and Postretirement Plans (Tables)	12 Months Ended
	Dec. 31, 2023
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Schedule of Defined Benefit Plans Disclosures	The following table sets forth the change in benefit obligation for the pension and postretirement benefit plans as of December 31, 2023: Pension United States of America United Kingdom Mexico Change in benefit obligation: Bargaining Salaried Supplemental Pension Pension Total Postretirement Benefit obligation at the beginning of year $ 474.9 $ 128.1 $ 15.5 $ 47.7 $ 0.4 $ 666.6 $ 87.4 Service cost 9.5 0.9 — — — 10.4 0.7 Interest cost 25.9 6.7 0.9 2.3 — 35.8 4.7 Actuarial (gains) losses 19.1 5.7 0.7 7.3 — 32.8 3.8 Benefits paid ( 38.5 ) ( 11.4 ) ( 0.6 ) ( 3.3 ) — ( 53.8 ) ( 11.7 ) Settlements — ( 6.0 ) — — — ( 6.0 ) — Foreign currency translation adjustment — — — 2.7 0.1 2.8 — Benefit obligation at the end of year $ 490.9 $ 124.0 $ 16.5 $ 56.7 $ 0.5 $ 688.6 $ 84.9 Significant actuarial losses related to changes in benefit obligations for 2023 primarily resulted from a decrease in discount rates. The following table sets forth the change in benefit obligation for the pension and postretirement benefit plans as of December 31, 2022: Pension United States of America United Kingdom Mexico Change in benefit obligation: Bargaining Salaried Supplemental Pension Pension Total Postretirement Benefit obligation at the beginning of year $ 1,025.4 $ 187.4 $ 23.6 $ 82.4 $ 0.4 $ 1,319.2 $ 117.8 Service cost 13.9 0.3 — — — 14.2 1.1 Interest cost 31.1 6.5 0.7 1.3 — 39.6 3.4 Actuarial (gains) losses ( 203.6 ) ( 34.0 ) ( 6.5 ) ( 25.3 ) — ( 269.4 ) ( 24.0 ) Benefits paid ( 51.0 ) ( 11.6 ) ( 0.6 ) ( 2.5 ) — ( 65.7 ) ( 10.9 ) Settlements ( 340.9 ) ( 20.5 ) ( 1.7 ) — — ( 363.1 ) — Foreign currency translation adjustment — — — ( 8.2 ) — ( 8.2 ) — Benefit obligation at the end of year $ 474.9 $ 128.1 $ 15.5 $ 47.7 $ 0.4 $ 666.6 $ 87.4 Significant actuarial gains related to changes in benefit obligations for 2022 primarily resulted from an increase in discount rates. Significant settlements were a result of the Bargaining Plan annuity purchase as well as lump sum payments during 2022. The following table sets forth the change in plan assets and funded status for the pension and postretirement benefit plan as of December 31, 2023: Pension United States of America United Kingdom Mexico Change in plan assets: Bargaining Salaried Supplemental Pension Pension Total Postretirement Fair value of plan assets at the beginning of year $ 353.9 $ 137.7 $ — $ 57.5 $ 0.3 $ 549.4 $ 59.2 Actual return on plan assets 19.3 9.3 — 2.5 — 31.1 5.3 Company contributions / payments — — 0.6 1.2 — 1.8 1.0 Benefits paid ( 38.5 ) ( 11.4 ) ( 0.6 ) ( 3.3 ) — ( 53.8 ) ( 11.7 ) Settlements — ( 6.0 ) — — — ( 6.0 ) — Foreign currency translation adjustment — — — 3.1 — 3.1 — Fair value of plan assets at end of year $ 334.7 $ 129.6 $ — $ 61.0 $ 0.3 $ 525.6 $ 53.8 Funded status at end of year $ ( 156.2 ) $ 5.6 $ ( 16.5 ) $ 4.3 $ ( 0.2 ) $ ( 163.0 ) $ ( 31.1 ) The following table sets forth the change in plan assets and funded status for the pension and postretirement benefit plan as of December 31, 2022: Pension United States of America United Kingdom Mexico Change in plan assets: Bargaining Salaried Supplemental Pension Pension Total Postretirement Fair value of plan assets at the beginning of year $ 862.8 $ 205.7 $ — $ 107.2 $ 0.3 $ 1,176.0 $ 76.8 Actual return on plan assets ( 119.7 ) ( 35.9 ) — ( 38.0 ) — ( 193.6 ) ( 8.8 ) Company contributions / payments — — 2.3 1.3 — 3.6 2.1 Benefits paid ( 51.0 ) ( 11.6 ) ( 0.6 ) ( 2.5 ) — ( 65.7 ) ( 10.9 ) Settlements ( 338.2 ) ( 20.5 ) ( 1.7 ) — — ( 360.4 ) — Foreign currency translation adjustment — — — ( 10.5 ) — ( 10.5 ) — Fair value of plan assets at end of year $ 353.9 $ 137.7 $ — $ 57.5 $ 0.3 $ 549.4 $ 59.2 Funded status at end of year $ ( 121.0 ) $ 9.6 $ ( 15.5 ) $ 9.8 $ ( 0.1 ) $ ( 117.2 ) $ ( 28.2 ) The Bargaining Plan, Salaried Plan, and Supplemental Plan have a provision that permits employees to elect to receive their pension benefits in a lump sum upon retirement. The Company's accounting policy is to recognize settlements during the quarter in which it is projected that the costs of all settlements during the year will be greater than the sum of the service cost and interest cost components. In the first quarter of 2023, in anticipation of receiving the regulatory approval to move forward with the plan termination process, the cumulative costs of all lump sum payments and other settlements were projected to exceed this threshold during 2023 for the Salaried Plan. Ultimately, these costs did not exceed this threshold for the Salaried Plan during 2023. The Salaried Plan's pension obligations and plan assets were remeasured during each quarter of 2023. In the first quarter of 2022, the cumulative cost of all lump sum payments exceeded this threshold for the Supplemental Plan. Additionally, in the first quarter of 2022, the cumulative costs of all lump sum payments were projected to exceed this threshold during 2022 for the Salaried Plan. These costs did ultimately exceed this threshold for the Salaried Plan during the second quarter of 2022. Also, during the second quarter of 2022, the cumulative costs of all lump sum payments were projected to exceed this threshold in 2022 for the Bargaining Plan. These costs did ultimately exceed this threshold for the Bargaining Plan during the third quarter of 2022. These payments constitute a partial settlement, which is a significant event requiring remeasurement of both plan assets and benefit obligations. As a result, the Company completed a full remeasurement of its pension obligations and plan assets associated with the Supplemental Plan during the first quarter of 2022. No further remeasurement was required in 2022 related to the Supplemental Plan, as no further lump sum payments were made. The Salaried Plan's pension obligations and plan assets were remeasured during each quarter of 2022. We also completed a full remeasurement of the Bargaining Plan's pension obligations and plan assets during the second, third, and fourth quarters of 2022.
Schedule of Amounts Recognized in Balance Sheet	Amounts recognized on the balance sheet at December 31, 2023 for the Company's pension and postretirement benefit plans include: Pension United States of America United Kingdom Mexico Bargaining Salaried Supplemental Pension Pension Total Postretirement Non-current assets $ — $ 5.6 $ — $ 4.3 $ — $ 9.9 $ — Current liabilities ( 41.7 ) — ( 0.6 ) — — ( 42.3 ) ( 1.2 ) Non-current liabilities ( 114.5 ) — ( 15.9 ) — ( 0.2 ) ( 130.6 ) ( 29.9 ) Total $ ( 156.2 ) $ 5.6 $ ( 16.5 ) $ 4.3 $ ( 0.2 ) $ ( 163.0 ) $ ( 31.1 ) Amounts recognized on the balance sheet at December 31, 2022 for the Company's pension and postretirement benefit plans include: Pension United States of America United Kingdom Mexico Bargaining Salaried Supplemental Pension Pension Total Postretirement Non-current assets $ — $ 9.6 $ — $ 9.8 $ — $ 19.4 $ — Current liabilities — — ( 0.6 ) — — ( 0.6 ) ( 1.4 ) Non-current liabilities ( 121.0 ) — ( 15.0 ) — ( 0.1 ) ( 136.1 ) ( 26.8 ) Total $ ( 121.0 ) $ 9.6 $ ( 15.6 ) $ 9.8 $ ( 0.1 ) $ ( 117.3 ) $ ( 28.2 )
Schedule of Amounts Recognized in Other Comprehensive Income (Loss)	Included in accumulated other comprehensive income (loss) at December 31, 2023 were the following before-tax amounts that had not been recognized in net periodic benefit cost: Pension United States of America United Kingdom Mexico Bargaining Salaried Supplemental Pension Pension Total Postretirement Unrecognized prior service (benefit) cost $ 11.1 $ — $ — $ 0.5 $ — $ 11.6 $ ( 44.0 ) Included in accumulated other comprehensive income (loss) at December 31, 2022 were the following before-tax amounts that had not been recognized in net periodic benefit cost: Pension United States of America United Kingdom Mexico Bargaining Salaried Supplemental Pension Pension Total Postretirement Unrecognized prior service (benefit) cost $ 12.4 $ — $ — $ 0.5 $ — $ 12.9 $ ( 49.9 )
Schedule of Assumptions Used	The weighted average assumptions used in determining benefit obligation as of December 31, 2023 and 2022 were as follows: Pension Postretirement Assumptions: 2023 2022 2023 2022 Discount rate 5.33 % 5.61 % 5.43 % 5.70 % Future compensation assumption 3.00 % 3.00 % n/a n/a The weighted average assumptions used in determining benefit cost for the years ended December 31, 2023 and 2022 were as follows: Pension Postretirement Assumptions: 2023 2022 2023 2022 Discount rate 5.61 % 2.96 % 5.70 % 3.00 % Future compensation assumption 3.00 % 3.00 % n/a n/a Expected long-term return on plan assets 7.13 % 5.96 % 6.25 % 4.75 %
Schedule of Periodic Benefit Cost	The components of net periodic benefit cost (income) for the year ended December 31, 2023 were as follows: Pension United States of America United Kingdom Mexico Components of net periodic benefit cost (income): Bargaining Salaried Supplemental Pension Pension Total Postretirement Service cost $ 9.5 $ 0.9 $ — $ — $ — $ 10.4 $ 0.7 Interest cost 25.9 6.7 0.9 2.3 — 35.8 4.7 Expected return on plan assets ( 26.9 ) ( 7.5 ) — ( 2.7 ) — ( 37.1 ) ( 3.4 ) Amortization of prior service cost 1.3 — — — — 1.3 ( 6.0 ) Settlements — — — — — — — Net remeasurement losses (gains) 26.6 4.0 0.6 7.5 — 38.7 1.9 Net Periodic Benefit Cost (Income) $ 36.4 $ 4.1 $ 1.5 $ 7.1 $ — $ 49.1 $ ( 2.1 ) The components of net periodic benefit cost (income) for the year ended December 31, 2022 were as follows: Pension United States of America United Kingdom Mexico Components of net periodic benefit cost (income): Bargaining Salaried Supplemental Pension Pension Total Postretirement Service cost $ 13.9 $ 0.3 $ — $ — $ — $ 14.2 $ 1.1 Interest cost 31.1 6.5 0.7 1.3 — 39.6 3.4 Expected return on plan assets ( 46.7 ) ( 5.0 ) — ( 3.2 ) — ( 54.9 ) ( 3.4 ) Amortization of prior service cost 1.3 — — — — 1.3 ( 6.0 ) Settlements ( 2.7 ) — — — — ( 2.7 ) — Net remeasurement losses (gains) ( 37.2 ) 6.9 ( 6.5 ) 15.9 — ( 20.9 ) ( 11.8 ) Net Periodic Benefit Cost (Income) $ ( 40.3 ) $ 8.7 $ ( 5.8 ) $ 14.0 $ — $ ( 23.4 ) $ ( 16.7 ) The components of net periodic benefit cost (income) for the year ended December 31, 2021 were as follows: Pension United States of America United Kingdom Mexico Components of net periodic benefit cost (income): Bargaining Salaried Supplemental Pension Pension Total Postretirement Service cost $ 17.0 $ 0.4 $ — $ — $ — $ 17.4 $ 1.2 Interest cost 28.4 5.9 0.8 1.1 — 36.2 3.2 Expected return on plan assets ( 51.5 ) ( 12.6 ) — ( 3.3 ) — ( 67.4 ) ( 3.4 ) Amortization of prior service cost 0.2 — — — — 0.2 ( 6.0 ) Curtailment — — — — — — — Net remeasurement losses (gains) ( 15.1 ) 2.5 ( 1.5 ) ( 1.1 ) — ( 15.2 ) ( 4.9 ) Net Periodic Benefit Cost (Income) $ ( 21.0 ) $ ( 3.8 ) $ ( 0.7 ) $ ( 3.3 ) $ — $ ( 28.8 ) $ ( 9.9 ) Metallus
Schedule of Target Allocations for each Plan's Assets	The target allocations for each plan's assets are as follows: Pension United States of America United Kingdom Mexico Target Allocations: Bargaining Salaried Supplemental Pension Pension Weighted Postretirement Equity securities 38.0 % — n/a 17.5 % — 26.2 % 26.0 % Debt securities 34.0 % 100.0 % n/a 65.0 % 100.0 % 53.9 % 67.0 % Other investments 28.0 % — n/a 17.5 % — 19.9 % 7.0 %
Schedule of Allocation of Plan Assets	The following table presents the fair value hierarchy for those investments of the Company's pension assets measured at fair value on a recurring basis as of December 31, 2023: Total Level 1 Level 2 Level 3 Assets: Cash and cash equivalents $ 5.8 $ — $ 5.8 $ — U.S government and agency securities 59.8 50.7 9.1 — Corporate bonds 39.8 — 39.8 — Mutual fund - equities 83.3 83.3 — — Mutual fund - fixed income 12.2 12.2 — — Mutual fund - tactical tilt 10.6 10.6 — — Real estate 14.1 — — 14.1 Private debt 25.7 — — 25.7 Other 0.6 — 0.6 — Total Assets in the fair value hierarchy $ 251.9 $ 156.8 $ 55.3 $ 39.8 Assets measured at net asset value (1) 273.7 — — — Total Assets $ 525.6 $ 156.8 $ 55.3 $ 39.8 (1) Certain assets that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. Such assets include common collective trusts that invest in equity securities and fixed income securities, limited partnerships, real estate partnerships, and hedge funds. As of December 31, 2023 , these assets are redeemable at net asset value within 90 days, except for certain private investments with an estimated liquidation period of one to ten years. The following table presents the fair value hierarchy for those investments of the Company's pension assets measured at fair value on a recurring basis as of December 31, 2022: Total Level 1 Level 2 Level 3 Assets: Cash and cash equivalents $ 58.4 $ 3.0 $ 55.4 $ — U.S government and agency securities 53.7 49.4 4.3 — Corporate bonds 113.0 — 113.0 — Equity securities 14.5 14.5 — — Real estate 7.6 — — 7.6 Private debt 18.8 — — 18.8 Total Assets in the fair value hierarchy $ 266.0 $ 66.9 $ 172.7 $ 26.4 Assets measured at net asset value (1) 283.4 — — — Total Assets $ 549.4 $ 66.9 $ 172.7 $ 26.4 (1) Certain assets that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. Such assets include common collective trusts that invest in equity securities and fixed income securities, limited partnerships, real estate partnerships, and hedge funds. As of December 31, 2022 , these assets were redeemable at net asset value within 90 days. The following table sets forth a summary of changes in the fair value of the Company's pension plan level three assets for the year ended December 31, 2023: Level 3 assets only 2023 Balance at the beginning of year $ 26.4 Transfers in and/or out of Level 3 — Actual return on plan assets: Realized gain (loss) ( 0.6 ) Net unrealized gain (loss) 2.1 Purchases, sales, issuances and settlements: Purchases 14.3 Sales ( 2.4 ) Balance at the end of year $ 39.8 The following table presents the fair value hierarchy for those investments of the Company's postretirement assets measured at fair value on a recurring basis as of December 31, 2023: Total Level 1 Level 2 Level 3 Assets: Cash and cash equivalents $ 2.2 $ 2.2 $ — $ — Mutual fund - equities 13.5 13.5 — — Mutual fund - fixed income 7.3 7.3 — — Mutual fund - real assets 1.1 1.1 — — Mutual fund - tactical tilt 2.5 2.5 — — Total Assets in the fair value hierarchy $ 26.6 $ 26.6 $ — $ — Assets measured at net asset value (1) 27.2 — — — Total Assets $ 53.8 $ 26.6 $ — $ — (1) Certain assets that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. Such assets include common collective trusts that invest in equity securities and fixed income securities. As of December 31, 2023, these assets are redeemable at net asset value on a daily basis. The following table presents the fair value hierarchy for those investments of the Company's postretirement assets measured at fair value on a recurring basis as of December 31, 2022: Total Level 1 Level 2 Level 3 Assets: Cash and cash equivalents $ 1.4 $ 1.4 $ — $ — Mutual fund - fixed income 4.7 4.7 — — Total Assets in the fair value hierarchy $ 6.1 $ 6.1 $ — $ — Assets measured at net asset value (1) 53.1 — — — Total Assets $ 59.2 $ 6.1 $ — $ — (1) Certain assets that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. Such assets include common collective trusts that invest in equity securities, fixed income securities, and limited partnerships. As of December 31, 2022 , these assets were redeemable at net asset value within 90 days.
Schedule of Expected Benefit Payments	Future benefit payments are expected to be as follows: Pension United States of America United Kingdom Mexico Benefit Payments: Bargaining Salaried (1) Supplemental Pension Pension Total Postretirement 2024 39.4 30.3 0.6 2.8 — 73.1 9.7 2025 40.3 10.5 0.6 2.8 — 54.2 8.9 2026 43.1 10.1 0.5 2.7 — 56.4 8.3 2027 47.2 9.8 13.8 3.1 — 73.9 7.9 2028 46.7 9.5 0.5 3.2 — 59.9 7.5 2029-2033 206.9 41.4 2.0 18.6 — 268.9 33.1

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2023
Share-based Compensation, Stock Options, Activity	The following summarizes the Company's stock option activity from January 1, 2023 to December 31, 2023: Number of Weighted Weighted Aggregate Outstanding as of December 31, 2022 1,119,523 $ 18.85 Granted — — — — Exercised ( 291,928 ) 10.11 — — Canceled, forfeited or expired ( 206,245 ) 33.93 — — Outstanding as of December 31, 2023 621,350 $ 17.95 3.5 $ 5.6 Options expected to vest 66,360 5.26 6.2 1.2 Options exercisable 554,990 $ 19.47 3.1 $ 4.4
Transformation Incentive Grant Program Activity	The following summarizes the Company's Transformation Incentive Grant Program activity from January 1, 2023 to December 31, 2023: Number of Weighted Outstanding as of December 31, 2022 — $ — Granted (Tier 1-2) 200,000 22.22 Granted (Tier 3-4) 150,000 22.78 Canceled, forfeited or expired — — Outstanding as of December 31, 2023 350,000 $ 22.46
Time-Based Restricted Stock Units
Nonvested Restricted Stock Shares Activity	The following summarizes the Company's stock-settled, time-based restricted stock unit activity from January 1, 2023 to December 31, 2023: Number of Weighted Outstanding as of December 31, 2022 1,546,002 $ 9.29 Granted 385,959 18.52 Vested ( 302,935 ) 11.41 Canceled, forfeited or expired ( 9,307 ) 18.19 Outstanding as of December 31, 2023 1,619,719 $ 11.99
Performance-Based Restricted Stock Units
Nonvested Restricted Stock Shares Activity	The following summarizes the Company's stock-settled performance-based restricted stock unit activity from January 1, 2023 to December 31, 2023: Number of Weighted Outstanding as of December 31, 2022 968,415 $ 10.21 Granted 211,639 23.13 Vested ( 167,694 ) 4.98 Canceled, forfeited or expired 2,298 23.44 Outstanding as of December 31, 2023 1,014,658 $ 13.76

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2023
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	Changes in accumulated other comprehensive income (loss) for the years ended December 31, 2023 and 2022 by component were as follows: Foreign Currency Pension and Total Balance as of December 31, 2022 $ ( 6.8 ) $ 21.5 $ 14.7 Other comprehensive income before reclassifications, before income tax — — — Amounts reclassified from accumulated other comprehensive income 0.3 ( 4.9 ) ( 4.6 ) Amounts deferred to accumulated other comprehensive income — 2.3 2.3 Tax effect — — — Net current period other comprehensive income (loss), net of income taxes 0.3 ( 2.6 ) ( 2.3 ) Balance as of December 31, 2023 $ ( 6.5 ) $ 18.9 $ 12.4 Foreign Currency Pension and Total Balance as of December 31, 2021 $ ( 5.1 ) $ 25.8 $ 20.7 Other comprehensive income before reclassifications, before income tax ( 1.7 ) — ( 1.7 ) Amounts reclassified from accumulated other comprehensive income — ( 4.7 ) ( 4.7 ) Amounts deferred to accumulated other comprehensive income — — — Tax effect — 0.4 0.4 Net current period other comprehensive income (loss), net of income taxes ( 1.7 ) ( 4.3 ) ( 6.0 ) Balance as of December 31, 2022 $ ( 6.8 ) $ 21.5 $ 14.7

Basis of Presentation - Narrati

Basis of Presentation - Narrative (Details) Tons in Millions, T in Millions	12 Months Ended
	Dec. 31, 2023 Tons T
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Annual Melt Capacity | T	1.2
Annual Shipment Capacity | Tons	0.9

Significant Accounting Polici_3

Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions		12 Months Ended
	Dec. 15, 2023	Dec. 31, 2023	Dec. 31, 2022
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Subsequent pricing adjustments		$ 16
Restricted Cash		$ 0.7	$ 0.6
Building
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Useful lives of property, plant and equipment, net		30 years
Minimum [Member] | Machinery and Equipment
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Useful lives of property, plant and equipment, net		3 years
Minimum [Member] | Performance-Based Restricted Stock Units
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Vesting Percentage	0%	0%
Maximum [Member] | Machinery and Equipment
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Useful lives of property, plant and equipment, net		20 years
Maximum [Member] | Performance-Based Restricted Stock Units
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Vesting Percentage	200%	200%

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 1,362.4	$ 1,329.9	$ 1,282.9
Long-lived assets, net	506.6	503.6
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	1,239.4	1,201.3	1,166.1
Long-lived assets, net	506.2	503
Foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	123	128.6	$ 116.8
Long-lived assets, net	$ 0.4	$ 0.6

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Net sales		$ 1,362.4	$ 1,329.9	$ 1,282.9
Bar
Disaggregation of Revenue [Line Items]
Net sales		917.1	887.4	863.6
Tube
Disaggregation of Revenue [Line Items]
Net sales		170.1	173.7	164.4
Manufactured Components
Disaggregation of Revenue [Line Items]
Net sales		253.4	243.3	224
Other
Disaggregation of Revenue [Line Items]
Net sales	[1]	21.8	25.5	30.9
Industrial
Disaggregation of Revenue [Line Items]
Net sales		533.3	549	601
Automotive
Disaggregation of Revenue [Line Items]
Net sales		531.9	539.1	527.9
Aerospace & Defense
Disaggregation of Revenue [Line Items]
Net sales	[2]	115	79.7	60.2
Energy
Disaggregation of Revenue [Line Items]
Net sales		160.4	136.6	62.9
Other
Disaggregation of Revenue [Line Items]
Net sales	[3]	$ 21.8	$ 25.5	$ 30.9
[1] “Other” for sales by product type relates to the Company’s scrap sales. “Aerospace & Defense” sales by end-market were previously included in "Industrial." “Other” sales by end-market includes the Company’s scrap sales.

Revenue Recognition - Narrative

Revenue Recognition - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Contract liabilities totalated	$ 0.8	$ 3.6

Restructuring Charges - Narrati

Restructuring Charges - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Restructuring and Related Activities [Abstract]
Restructuring charges	$ 0	$ 0.8	$ 6.7

Restructuring Charges - Summary

Restructuring Charges - Summary of Restructuring Reserve (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Restructuring Reserve [Roll Forward]
Beginning balance	$ 0.5	$ 4.7
Expenses	0	0.8	$ 6.7
Payments	(0.5)	(5)
Ending balance	$ 0	$ 0.5	$ 4.7

Disposition of Non-Core Assets

Disposition of Non-Core Assets (Details) $ in Millions	3 Months Ended					12 Months Ended			15 Months Ended
	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($) Program	Sep. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2023 USD ($)
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal, Statement of Income or Comprehensive Income [Extensible Enumeration]	Property, plant and equipment, net
Impairment, Long-Lived Asset, Held-for-Use, Statement of Income or Comprehensive Income [Extensible Enumeration]					Impairment charges
Proceeds from sale of consolidated subsidiary, net						$ 0	$ 0	$ 6.2
Loss on sale of consolidated subsidiary						0	0	1.1
Proceeds from disposals of property, plant and equipment						1.7	5.4	1.2
Early termination reimbursement from customer		$ 4.3
TimkenSteel (Shanghai) Corporation Limited | Daido Steel (Shanghai) Co., Ltd.
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Proceeds from sale of consolidated subsidiary, net				$ 6.2
Loss on sale of consolidated subsidiary				$ (1.1)
Harrison Facility | Melt and Cast Related Assets
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Non-cash charges related to write down of assets					$ 9.5
St.Clair Facility
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Inventory write-down								0.2
Impairment charges								2.4
Capital recovery remaining amount to be recognized			$ 1.1
Number of customer program early termination | Program			2
Machinery and Equipment | Harrison Facility | Melt and Cast Related Assets
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Non-cash charges related to write down of assets					7.9
Spare Parts | Harrison Facility | Melt and Cast Related Assets
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Non-cash charges related to write down of assets					$ 1.6
Disposal Group, Held-for-sale, Not Discontinued Operation
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Assets held for sale			$ 4.3					$ 4.3
Net cash proceeds		2.8					2.8
Loss on sale of assets		$ 1.5					1.5
Disposal Group, Held-for-sale, Not Discontinued Operation | Machinery and Equipment
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (loss) on sale/disposal	$ 3.4
Proceeds from disposals of property, plant and equipment						$ 1.7	$ 1.7		$ 3.4
Disposal Group Not Discontinued Operation Additional Payment Date Description						The final payment resulted in a gain on disposal of assets of $3.4 million in the second quarter of 2023. The gain, which has been recognized in the Consolidated Statement of Operations, was partially offset by write-offs of aged assets removed from service throughout 2023.

Other (Income) Expense, net - S

Other (Income) Expense, net - Schedule of Other (Income) Expense, Net (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other Income and Expenses [Abstract]
Pension and postretirement non-service benefit (income) loss			$ (4.6)	$ (20.3)	$ (37.2)
Loss (gain) from remeasurement of benefit plans			40.6	(35.4)	(20.1)
Foreign currency exchange loss (gain)			0	(0.2)	0.1
Insurance recoveries	$ (33)	$ (1.5)	(31.3)	(34.5)	0
Sales and use tax refund			(1.4)	0	(2.5)
Miscellaneous (income) expense			0.4	(0.2)	0.2
Total other (income) expense, net			$ 3.7	$ (90.6)	$ (59.5)

Other (Income) Expense, net - N

Other (Income) Expense, net - Narrative (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statutory Accounting Practices [Line Items]
Sales and use tax refund					$ 1.4	$ 0	$ 2.5
Loss (gain) from remeasurement of benefit plans					40.6	(35.4)	(20.1)
Increase in liability					36.6
Decrease in liability						359.9	55.7
Investment losses on plan assets					4	327.2	35.6
Lump sum based loss						327.2
Gain on insurance proceeds received			$ 33	$ 1.5	31.3	34.5	$ 0
Total recovery		$ 20	$ 13		$ 11.3
Non cash settlement related to bargaining plan						$ 2.7
Subsequent Event
Statutory Accounting Practices [Line Items]
Total recovery	$ 20

Income Tax Provision - Income f

Income Tax Provision - Income from Operations Before Income Taxes Based on Geographic Location of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
United States	$ 103.2	$ 108.5	$ 171.2
Non-United States	(6.8)	(11.4)	5.5
Income (loss) from operations before income taxes	$ 96.4	$ 97.1	$ 176.7

Income Tax Provision - (Benefit

Income Tax Provision - (Benefit) Provision for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current:
Federal	$ 30.4	$ 0.6	$ 0.2
State and local	6.1	5.7	3.7
Foreign	0.2	0.8	0.6
Total current tax expense (benefit)	36.7	7.1	4.5
Deferred:
Federal	(9.2)	24.2	0.8
State and local	(0.5)	0.7	0.3
Foreign	0	0	0.1
Total deferred tax expense (benefit)	(9.7)	24.9	1.2
Provision (benefit) for incomes taxes	$ 27	$ 32	$ 5.7

Income Tax Provision - Narrativ

Income Tax Provision - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Loss Carryforwards [Line Items]
Income Taxes Receivable, Current	$ 0.3	$ 2.2
Open tax year	2019 2020 2021 2022
Deferred income taxes	$ 15	25.9
Unrecognized Tax Benefits	0	0	$ 0
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	0	0	0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	0	0	$ 0
Foreign
Operating Loss Carryforwards [Line Items]
Income Taxes Paid	1.4	0.2
Operating Loss Carryforwards	59.5
State and Local
Operating Loss Carryforwards [Line Items]
Income Taxes Paid	4.9	5
Operating Loss Carryforwards	15.8
U.S.
Operating Loss Carryforwards [Line Items]
Income Taxes Paid	19	$ 2
Operating Loss Carryforwards	$ 0

Income Tax Provision - Reconcil

Income Tax Provision - Reconciliation Between Effective Tax Rate and Statutory Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
U.S. federal income tax provision (benefit) at statutory rate	$ 20.2	$ 20.4	$ 37.1
Adjustments:
State and local income taxes, net of federal tax benefit	4.2	8.4	4.1
Permanent differences	1.2	8.9	(0.2)
Foreign earnings taxed at different rates	0	(3.6)	(0.5)
Valuation allowance	1.8	(2.5)	(34.8)
U.S. research tax credit	(0.3)	(0.6)	0
Other items, net	(0.1)	1	0
Provision (benefit) for incomes taxes	$ 27	$ 32	$ 5.7
Effective tax rate	28%	32.90%	3.20%

Income Tax Provision - Effect o

Income Tax Provision - Effect of Temporary Differences Giving Rise to Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Deferred tax liabilities:
Depreciation	$ (75)	$ (81.4)
Inventory	0	0
Prepaid insurance	(1.9)	0
Leases - right-of-use asset	(2.8)	(3.1)
Deferred tax liabilities	(79.7)	(84.5)
Deferred tax assets:
Tax loss carryforwards	16	20.5
Pension and postretirement benefits	46.8	35.5
Other employee benefit accruals	8	6.6
Lease liability	2.8	3.1
State decoupling	1.2	0.8
Accrued restructuring	0	0.1
Capital loss carryforward	0.8	0.8
Intangible assets	0.1	0.2
Inventory	0.8	0.7
Allowance for doubtful accounts	0.5	0.3
Accrued Legal	0	2
Capitalized R&D	3.2	0.9
Other, net	0	0.1
Deferred tax assets subtotal	80.2	71.6
Valuation allowances	(15.5)	(13)
Deferred tax assets	64.7	58.6
Net deferred tax assets (liabilities)	$ (15)	$ (25.9)

Earnings (Loss) Per Share - Add

Earnings (Loss) Per Share - Additional Information (Details) - USD ($) shares in Millions	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2023	Jun. 30, 2022	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares assumed purchased				3	3.2	3
Shares assumed purchased with potential proceeds				0.9	1.1	1.3
Repurchase of convertible notes				$ 18,700,000	$ 67,600,000	$ 38,900,000
Convertible Senior Notes due 2025 [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of computation of diluted earnings (loss) per share				0.7	2.3
Convertible notes repurchased outstanding principal amount	$ 7,500,000	$ 25,200,000	$ 0
Repurchase of convertible notes	18,700,000	67,600,000
Debt Instrument, Face Amount	$ 7,500,000	$ 25,200,000			$ 0
Convertible Notes [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of computation of diluted earnings (loss) per share				1.9
Employee Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of computation of diluted earnings (loss) per share				0.4	0.8	1.8
Equity-based Awards [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of computation of diluted earnings (loss) per share				3.4	4	4.8

Earnings (Loss) Per Share - Sch

Earnings (Loss) Per Share - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net income (loss), basic	$ 69.4	$ 65.1	$ 171
Add convertible notes interest	1	1.9	4.1
Net income (loss), diluted	$ 70.4	$ 67	$ 175.1
Denominator:
Weighted average shares outstanding, basic (in shares)	43.8	45.8	45.9
Dilutive effect of equity-based awards (in shares)	2.1	2.1	1.7
Dilutive effect of convertible notes (in shares)	1.9	3.6	7.4
Weighted average shares outstanding, diluted (in shares)	47.8	51.5	55
Basic earnings (loss) per share	$ 1.58	$ 1.42	$ 3.73
Diluted earnings (loss) per share	$ 1.47	$ 1.3	$ 3.18

Inventories - Schedule of Inven

Inventories - Schedule of Inventory (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Inventory Disclosure [Abstract]
Manufacturing supplies	$ 51.5	$ 36.9
Raw materials	17.5	23.9
Work in process	109.6	94.7
Finished products	50.1	37.4
Gross inventory	228.7	192.9
Allowance for inventory reserves	(0.7)	(0.5)
Total inventories, net	$ 228	$ 192.4

Property, Plant and Equipment -

Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Land	$ 11.2	$ 11.2
Buildings and improvements	429.2	414.6
Machinery and equipment	1,367.6	1,391.5
Construction in progress	59.3	30.8
Subtotal	1,867.3	1,848.1
Less allowances for depreciation	(1,374.8)	(1,362)
Property, plant and equipment, net	$ 492.5	$ 486.1

Property, Plant and Equipment_2

Property, Plant and Equipment - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation	$ 54,600,000	$ 55,500,000	$ 59,800,000
Accelerated depreciation	0	0	1,500,000
Impairment charges and loss on sale	$ 2,500,000	$ 1,900,000	1,300,000
Impairment charges related to the indefinite idling of assets			$ 10,600,000

Property, Plant and Equipment_3

Property, Plant and Equipment - Schedule of Supplemental Cash Flow Information Related to Non-Cash Investing Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Supplemental Cash Flow Elements [Abstract]
Accrued property, plant and equipment purchases	$ 12.1	$ 10.6	$ 3.6

Intangible Assets - Schedule of

Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 70.9	$ 73.2
Accumulated Amortization	68.5	68.2
Net Carrying Amount	2.4	5
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6.3	6.3
Accumulated Amortization	6.3	6.2
Net Carrying Amount	0	0.1
Technology use
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	9	9
Accumulated Amortization	9	9
Net Carrying Amount	0	0
Capitalized software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	55.6	57.9
Accumulated Amortization	53.2	53
Net Carrying Amount	$ 2.4	$ 4.9

Intangible Assets - Narrative (

Intangible Assets - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining useful life	8 years
Amortization expense for intangible assets	$ 2,300,000	$ 2,800,000	$ 3,300,000
Loss on disposal of intangibles	$ 0	$ 0	$ 0
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining useful life	15 years
Technology use
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining useful life	15 years
Capitalized software
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining useful life	6 years

Intangible Assets - Estimated A

Intangible Assets - Estimated Annual Amortization Expense (Details) $ in Millions	Dec. 31, 2023 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2024	$ 1.3
2025	0.3
2026	0.2
2027	0.1
2028	$ 0.1

Leases - Narrative (Details)

Leases - Narrative (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Lessee, Lease, Description [Line Items]
Lessee, operating lease, option to extend	true
Extension term	1 year
Weighted average remaining lease term for operating leases	3 years 1 month 6 days
Weighted average discount rate used to measure operating lease liabilities	4.30%	3.10%
Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease term	1 year
Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease term	5 years

Leases - Lease Cost (Details)

Leases - Lease Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Operating lease cost	$ 7.3	$ 6.7	$ 8.2
Short-term lease cost	0.8	0.9	0.7
Total lease cost	$ 8.1	$ 7.6	$ 8.9

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Cash paid for amounts included in the measurement of operating lease liabilities	$ 7.1	$ 6.7	$ 8.2
Right-of-use assets obtained in exchange for operating lease obligations	$ 5.6	$ 4.5	$ 3.1

Leases - Future Minimum Lease P

Leases - Future Minimum Lease Payments (Details) $ in Millions	Dec. 31, 2023 USD ($)
Leases [Abstract]
2024	$ 5.5
2025	3.2
2026	1.7
2027	1.3
After 2028	0.8
Total future minimum lease payments	12.5
Less amount of lease payment representing interest	(1.1)
Total present value of lease payments	$ 11.4

Financing Arrangements - Summar

Financing Arrangements - Summary of Current and Non-current Debt (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Total debt	$ 13.2	$ 20.4
Less current portion of debt	13.2	20.4
Total non-current portion of debt	0	0
Credit Agreement
Debt Instrument [Line Items]
Total debt	0	0
Convertible Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Total debt	$ 13.2	$ 20.4

Financing Arrangements - Narrat

Financing Arrangements - Narrative (Details) $ / shares in Units, shares in Millions			3 Months Ended	6 Months Ended	12 Months Ended
	Jan. 01, 2024 USD ($) shares	Dec. 15, 2020 USD ($) $ / shares	Mar. 31, 2023 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2023 USD ($) Days shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($)	Feb. 15, 2024 USD ($)	Nov. 02, 2022 USD ($)	Dec. 20, 2021 shares
Debt Instrument [Line Items]
Settled with cash payment					$ 18,700,000	$ 67,600,000	$ 38,900,000
Loss on extinguishment of debt					11,400,000	43,100,000	0
Interest paid					2,100,000	3,100,000	5,100,000
Money market investment carrying value					139,700,000	209,500,000	0
Cash Held In Other Investments					119,900,000
Common Stock, Shares outstanding | shares										50
Stock Repurchase Program, Amount									$ 75,000,000
Average Repurchase price					$ 19.03	$ 17.18
Common Shares
Debt Instrument [Line Items]
Stock Repurchase Program, Amount							0
Stock Repurchased, Shares | shares					1.7	3
Stock Repurchased, Amount					$ 32,600,000	$ 52,000,000
Stock Repurchase Program, Remaining Amount					$ 40,400,000
Subsequent Event | Common Shares
Debt Instrument [Line Items]
Stock Repurchased, Shares | shares	0.1
Stock Repurchased, Amount	$ 1,200,000
Average Repurchase price	$ 21.07
Stock Repurchase Program, Remaining Amount								$ 39,200,000
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Variable interest rate, spread					0%
Third Amended Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date					Sep. 30, 2027
Fourth Amended Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity					$ 400,000,000
Line of credit facility, tentative future commitment increase					$ 100,000,000
Variable interest rate, spread					1%
Line of credit facility, unused capacity, commitment fee percentage					0.25%
Convertible Senior Notes due 2021
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 13,300,000
Convertible Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Maturity date		Dec. 01, 2025
Terms of conversion					The Convertible Senior Notes due 2025 are convertible at the option of the holders in certain circumstances and during certain periods into the Company's common shares, cash, or a combination thereof, at the Company's election.
Debt Instrument, Face Amount			$ 7,500,000	$ 25,200,000		0
Settled with cash payment			18,700,000	67,600,000
Debt instrument, threshold trading days | Days					20
Debt Instrument, threshold consecutive trading days | Days					30
Debt Instrument, threshold Percentage of stock price conversion					130%
Loss on extinguishment of debt			11,400,000	43,000,000
Unamortized debt issuance cost			$ 200,000	$ 600,000
Debt instrument, interest rate, stated percentage		6%
Debt instrument interest payment dates description		June 1 and December 1 of each year, beginning on December 1, 2021
Debt instrument, convertible, conversion price | $ / shares		$ 7.82
Debt instrument, convertible, conversion ratio		0.1278119
Debt instrument, convertible, amounts by which instrument can be converted		$ 1,000
Transaction costs, debt gross					$ 1,500,000
Fair value of convertible notes					41,500,000	53,400,000
Outstanding borrowings					0	$ 0	$ 0
Credit Agreement | Third Amended Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, tentative future commitment increase					258,800,000
Commercial and Standby Letters of Credit | Fourth Amended Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, borrowing sublimit					15,000,000
Swingline Loans | Fourth Amended Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, borrowing sublimit					40,000,000
First In, Last Out (FILO) | Fourth Amended Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, tentative future commitment increase					$ 30,000,000

Financing Arrangements - Schedu

Financing Arrangements - Schedule of Convertible Debt (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Total debt	$ 13.2	$ 20.4
Convertible Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Principal	13.3	20.8
Less: Debt issuance costs, net of amortization	(0.1)	(0.4)
Less: Debt discount, net of amortization	0	0
Total debt	$ 13.2	$ 20.4

Financing Arrangements - Sche_2

Financing Arrangements - Schedule Components of Interest Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Disclosure [Abstract]
Interest expense	$ 2.7	$ 3.9	$ 6.2
Interest income	(9.8)	(3.3)	(0.3)
Interest (income) expense, net	$ (7.1)	$ 0.6	$ 5.9

Financing Arrangements - Sche_3

Financing Arrangements - Schedule of Interest Expense (Details) - Convertible Notes - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Contractual interest expense	$ 0.9	$ 1.7	$ 3.7
Amortization of debt issuance costs	0.1	0.1	0.4
Total	$ 1	$ 1.8	$ 4.1

Retirement and Postretirement_3

Retirement and Postretirement Plans - Narrative (Details) - USD ($) $ in Millions			1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 01, 2023	Jul. 07, 2022	Oct. 29, 2021	Mar. 31, 2023	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined contribution plan cost						$ 3.4	$ 3.3	$ 2.8
Bargaining Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan term of contract			4 years
Defined benefit plan contract expiration date			Sep. 27, 2025
Increased in pension liability								14.2
Bargaining Plan's obligations	$ 40	$ 256.2		$ 25
Settlement gain					$ 2.7
Accumulated benefit obligation for plans which the accumulated benefit obligation exceeded the fair value of plan assets						486.1
Postretirement
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement gain						$ (1.9)	11.8	4.9
Benefit plan terminated effective date						Mar. 31, 2022
Expected annuity purchase year						2024
Expected contributions and payments from 2024 through 2032						$ 33.1
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement gain						(38.7)	20.9	$ 15.2
Retirement plan expenses						2.9	5.1
Accumulated benefit obligation						683.7	$ 660.6
Expected contributions and payments from 2024 through 2032						268.9
Supplemental Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated benefit obligation for plans which the accumulated benefit obligation exceeded the fair value of plan assets						16.6
Pension and Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected contributions and payments in next 12 months						45.5
Expected contributions and payments from 2024 through 2032						$ 177

Retirement and Postretirement_4

Retirement and Postretirement Plans - Change in Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension
Change in benefit obligation:
Benefit obligation at the beginning of year	$ 666.6	$ 1,319.2
Service cost	10.4	14.2	$ 17.4
Interest cost	35.8	39.6	36.2
Actuarial (gains) losses	32.8	(269.4)
Benefits paid	(53.8)	(65.7)
Settlements	(6)	(363.1)
Foreign currency translation adjustment	2.8	(8.2)
Benefit obligation at the end of year	688.6	666.6	1,319.2
Pension | United States of America | Bargaining Plan
Change in benefit obligation:
Benefit obligation at the beginning of year	474.9	1,025.4
Service cost	9.5	13.9	17
Interest cost	25.9	31.1	28.4
Actuarial (gains) losses	19.1	(203.6)
Benefits paid	(38.5)	(51)
Settlements	0	(340.9)
Benefit obligation at the end of year	490.9	474.9	1,025.4
Pension | United States of America | Salaried Plan
Change in benefit obligation:
Benefit obligation at the beginning of year	128.1	187.4
Service cost	0.9	0.3	0.4
Interest cost	6.7	6.5	5.9
Actuarial (gains) losses	5.7	(34)
Benefits paid	(11.4)	(11.6)
Settlements	(6)	(20.5)
Benefit obligation at the end of year	124	128.1	187.4
Pension | United States of America | Supplemental Plan
Change in benefit obligation:
Benefit obligation at the beginning of year	$ 15.5	23.6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Liability, Defined Benefit Plan, Noncurrent
Interest cost	$ 0.9	0.7	0.8
Actuarial (gains) losses	0.7	(6.5)
Benefits paid	(0.6)	(0.6)
Settlements	0	(1.7)
Benefit obligation at the end of year	16.5	15.5	23.6
Pension | United Kingdom | Pension Scheme
Change in benefit obligation:
Benefit obligation at the beginning of year	47.7	82.4
Service cost			0
Interest cost	2.3	1.3	1.1
Actuarial (gains) losses	7.3	(25.3)
Benefits paid	(3.3)	(2.5)
Foreign currency translation adjustment	2.7	(8.2)
Benefit obligation at the end of year	56.7	47.7	82.4
Pension | Mexico | Pension Plan
Change in benefit obligation:
Benefit obligation at the beginning of year	0.4	0.4
Actuarial (gains) losses		0
Foreign currency translation adjustment	0.1
Benefit obligation at the end of year	0.5	0.4	0.4
Postretirement
Change in benefit obligation:
Benefit obligation at the beginning of year	87.4	117.8
Service cost	0.7	1.1	1.2
Interest cost	4.7	3.4	3.2
Actuarial (gains) losses	3.8	(24)
Benefits paid	(11.7)	(10.9)
Benefit obligation at the end of year	$ 84.9	$ 87.4	$ 117.8

Retirement and Postretirement_5

Retirement and Postretirement Plans - Change in Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Pension
Change in plan assets:
Fair value of plan assets at the beginning of year	$ 549.4	$ 1,176
Actual return on plan assets	31.1	(193.6)
Company contributions / payments	1.8	3.6
Benefits paid	(53.8)	(65.7)
Settlements	(6)	(360.4)
Foreign currency translation adjustment	3.1	(10.5)
Fair value of plan assets at end of year	525.6	549.4
Funded status at end of year	(163)	(117.2)
Pension | United States of America | Bargaining Plan
Change in plan assets:
Fair value of plan assets at the beginning of year	353.9	862.8
Actual return on plan assets	19.3	(119.7)
Benefits paid	(38.5)	(51)
Settlements	0	(338.2)
Fair value of plan assets at end of year	334.7	353.9
Funded status at end of year	(156.2)	(121)
Pension | United States of America | Salaried Plan
Change in plan assets:
Fair value of plan assets at the beginning of year	137.7	205.7
Actual return on plan assets	9.3	(35.9)
Benefits paid	(11.4)	(11.6)
Settlements	(6)	(20.5)
Fair value of plan assets at end of year	129.6	137.7
Funded status at end of year	5.6	9.6
Pension | United States of America | Supplemental Plan
Change in plan assets:
Company contributions / payments	0.6	2.3
Benefits paid	(0.6)	(0.6)
Settlements	0	(1.7)
Funded status at end of year	(16.5)	(15.5)
Pension | United Kingdom | Pension Scheme
Change in plan assets:
Fair value of plan assets at the beginning of year	57.5	107.2
Actual return on plan assets	2.5	(38)
Company contributions / payments	1.2	1.3
Benefits paid	(3.3)	(2.5)
Foreign currency translation adjustment	3.1	(10.5)
Fair value of plan assets at end of year	61	57.5
Funded status at end of year	4.3	9.8
Pension | Mexico | Pension Plan
Change in plan assets:
Fair value of plan assets at the beginning of year	0.3	0.3
Fair value of plan assets at end of year	0.3	0.3
Funded status at end of year	(0.2)	(0.1)
Postretirement
Change in plan assets:
Fair value of plan assets at the beginning of year	59.2	76.8
Actual return on plan assets	5.3	(8.8)
Company contributions / payments	1	2.1
Benefits paid	(11.7)	(10.9)
Fair value of plan assets at end of year	53.8	59.2
Funded status at end of year	$ (31.1)	$ (28.2)

Retirement and Postretirement_6

Retirement and Postretirement Plans - Amounts Recognized in the Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Non-current assets	$ 9.9	$ 19.4
Current liabilities	(43.5)	(2)
Non-current liabilities	(160.5)	(162.9)
Pension
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Non-current assets	9.9	19.4
Current liabilities	(42.3)	(0.6)
Non-current liabilities	(130.6)	(136.1)
Total assets (liabilities) recognized	(163)	(117.3)
Pension | United States of America | Bargaining Plan
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities	(41.7)
Non-current liabilities	(114.5)	(121)
Total assets (liabilities) recognized	(156.2)	(121)
Pension | United States of America | Salaried Plan
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Non-current assets	5.6	9.6
Total assets (liabilities) recognized	5.6	9.6
Pension | United States of America | Supplemental Plan
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities	(0.6)	(0.6)
Non-current liabilities	(15.9)	(15)
Total assets (liabilities) recognized	(16.5)	(15.6)
Pension | United Kingdom | Pension Scheme
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Non-current assets	4.3	9.8
Total assets (liabilities) recognized	4.3	9.8
Pension | Mexico | Pension Plan
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Non-current liabilities	(0.2)	(0.1)
Total assets (liabilities) recognized	(0.2)	(0.1)
Postretirement
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities	(1.2)	(1.4)
Non-current liabilities	(29.9)	(26.8)
Total assets (liabilities) recognized	$ (31.1)	$ (28.2)

Retirement and Postretirement_7

Retirement and Postretirement Plans - Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Pension
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Unrecognized prior service (benefit) cost	$ 11.6	$ 12.9
Pension | United States of America | Bargaining Plan
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Unrecognized prior service (benefit) cost	11.1	12.4
Pension | United Kingdom | Pension Scheme
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Unrecognized prior service (benefit) cost	0.5	0.5
Postretirement
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Unrecognized prior service (benefit) cost	$ (44)	$ (49.9)

Retirement and Postretirement_8

Retirement and Postretirement Plans - Weighted Average Assumptions (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Pension
Benefit Obligation
Discount rate	5.33%	5.61%
Future compensation assumption	3%	3%
Benefit Cost
Discount rate	5.61%	2.96%
Future compensation assumption	3%	3%
Expected long-term return on plan assets	7.13%	5.96%
Postretirement
Benefit Obligation
Discount rate	5.43%	5.70%
Benefit Cost
Discount rate	5.70%	3%
Expected long-term return on plan assets	6.25%	4.75%

Retirement and Postretirement_9

Retirement and Postretirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 10.4	$ 14.2	$ 17.4
Interest cost	35.8	39.6	36.2
Expected return on plan assets	(37.1)	(54.9)	(67.4)
Amortization of prior service cost	1.3	1.3	0.2
Settlements	0	(2.7)
Curtailments			0
Net remeasurement losses (gains)	38.7	(20.9)	(15.2)
Net Periodic Benefit Cost (Income)	49.1	(23.4)	(28.8)
Pension | United States of America | Bargaining Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	9.5	13.9	17
Interest cost	25.9	31.1	28.4
Expected return on plan assets	(26.9)	(46.7)	(51.5)
Amortization of prior service cost	1.3	1.3	0.2
Settlements	0	(2.7)
Net remeasurement losses (gains)	26.6	(37.2)	(15.1)
Net Periodic Benefit Cost (Income)	36.4	(40.3)	(21)
Pension | United States of America | Salaried Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.9	0.3	0.4
Interest cost	6.7	6.5	5.9
Expected return on plan assets	(7.5)	(5)	(12.6)
Curtailments			0
Net remeasurement losses (gains)	4	6.9	2.5
Net Periodic Benefit Cost (Income)	4.1	8.7	(3.8)
Pension | United States of America | Supplemental Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest cost	0.9	0.7	0.8
Curtailments			0
Net remeasurement losses (gains)	0.6	(6.5)	(1.5)
Net Periodic Benefit Cost (Income)	1.5	(5.8)	(0.7)
Pension | United Kingdom | Pension Scheme
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost			0
Interest cost	2.3	1.3	1.1
Expected return on plan assets	(2.7)	(3.2)	(3.3)
Net remeasurement losses (gains)	7.5	15.9	(1.1)
Net Periodic Benefit Cost (Income)	7.1	14	(3.3)
Pension | Mexico | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net remeasurement losses (gains)		0	0
Net Periodic Benefit Cost (Income)		0	0
Postretirement
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.7	1.1	1.2
Interest cost	4.7	3.4	3.2
Expected return on plan assets	(3.4)	(3.4)	(3.4)
Amortization of prior service cost	(6)	(6)	(6)
Net remeasurement losses (gains)	1.9	(11.8)	(4.9)
Net Periodic Benefit Cost (Income)	$ (2.1)	$ (16.7)	$ (9.9)

Retirement and Postretiremen_10

Retirement and Postretirement Plans - Schedule of Target Allocations for each Plan's Assets (Details)	Dec. 31, 2023
Pension | Equity securities
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	26.20%
Pension | Debt Securities
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	53.90%
Pension | Other Investments
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	19.90%
Pension | Bargaining Plan | United States of America | Equity securities
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	38%
Pension | Bargaining Plan | United States of America | Debt Securities
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	34%
Pension | Bargaining Plan | United States of America | Other Investments
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	28%
Pension | Salaried Plan | United States of America | Debt Securities
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	100%
Pension | Salaried Plan | United States of America | Other Investments
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	0%
Pension | Pension Scheme | United Kingdom | Equity securities
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	17.50%
Pension | Pension Scheme | United Kingdom | Debt Securities
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	65%
Pension | Pension Scheme | United Kingdom | Other Investments
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	17.50%
Pension | Pension Plan | Mexico | Debt Securities
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	100%
Postretirement | Equity securities
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	26%
Postretirement | Debt Securities
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	67%
Postretirement | Other Investments
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target asset allocation	7%

Retirement and Postretiremen_11

Retirement and Postretirement Plans - Allocation of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	$ 525.6	$ 549.4	$ 1,176
Pension | Level 1, 2 and 3
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	251.9	266
Pension | Level 1, 2 and 3 | Cash and cash equivalents
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	5.8	58.4
Pension | Level 1, 2 and 3 | U.S government and agency securities
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	59.8	53.7
Pension | Level 1, 2 and 3 | Corporate bonds
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	39.8	113
Pension | Level 1, 2 and 3 | Mutual fund - equities
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	83.3
Pension | Level 1, 2 and 3 | Mutual fund - fixed income
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	12.2
Pension | Level 1, 2 and 3 | Mutual fund - tactical tilt
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	10.6
Pension | Level 1, 2 and 3 | Equity securities
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets		14.5
Pension | Level 1, 2 and 3 | Real estate
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	14.1	7.6
Pension | Level 1, 2 and 3 | Private debt
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	25.7	18.8
Pension | Level 1, 2 and 3 | Other
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	0.6
Pension | Level 1
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	156.8	66.9
Pension | Level 1 | Cash and cash equivalents
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	0	3
Pension | Level 1 | U.S government and agency securities
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	50.7	49.4
Pension | Level 1 | Corporate bonds
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	0
Pension | Level 1 | Mutual fund - equities
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	83.3
Pension | Level 1 | Mutual fund - fixed income
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	12.2
Pension | Level 1 | Mutual fund - tactical tilt
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	10.6
Pension | Level 1 | Equity securities
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets		14.5
Pension | Level 1 | Real estate
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	0	0
Pension | Level 1 | Private debt
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	0
Pension | Level 1 | Other
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	0
Pension | Level 2
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	55.3	172.7
Pension | Level 2 | Cash and cash equivalents
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	5.8	55.4
Pension | Level 2 | U.S government and agency securities
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	9.1	4.3
Pension | Level 2 | Corporate bonds
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	39.8	113
Pension | Level 2 | Real estate
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	0	0
Pension | Level 2 | Private debt
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	0
Pension | Level 2 | Other
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	0.6
Pension | Level 3
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	39.8	26.4
Pension | Level 3 | Real estate
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	14.1	7.6
Pension | Level 3 | Private debt
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	25.7	18.8
Pension | Assets measured at net asset value
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	$ 273.7	$ 283.4
Redemption period	90 days	90 days
Postretirement
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	$ 53.8	$ 59.2	$ 76.8
Postretirement | Level 1, 2 and 3
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	26.6	6.1
Postretirement | Level 1, 2 and 3 | Cash and cash equivalents
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	2.2	1.4
Postretirement | Level 1, 2 and 3 | Mutual fund - equities
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	13.5
Postretirement | Level 1, 2 and 3 | Mutual fund - fixed income
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	7.3	4.7
Postretirement | Level 1, 2 and 3 | Mutual fund - tactical tilt
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	2.5
Postretirement | Level 1, 2 and 3 | Real estate
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	1.1
Postretirement | Level 1
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	26.6	6.1
Postretirement | Level 1 | Cash and cash equivalents
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	2.2	1.4
Postretirement | Level 1 | Mutual fund - equities
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	13.5
Postretirement | Level 1 | Mutual fund - fixed income
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	7.3	4.7
Postretirement | Level 1 | Mutual fund - tactical tilt
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	2.5
Postretirement | Level 1 | Real estate
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	1.1
Postretirement | Assets measured at net asset value
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Assets	$ 27.2	$ 53.1
Redemption period		90 days

Retirement and Postretiremen_12

Retirement and Postretirement Plans - Summary of Changes in the Fair Value of Pension Plan Level Three Assets (Details) - Pension $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets at the beginning of year	$ 549.4
Fair value of plan assets at end of year	525.6
Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets at the beginning of year	26.4
Transfers in and/or out of Level 3	0
Realized gain (loss)	(0.6)
Net unrealized gain (loss)	2.1
Purchases	14.3
Sales	(2.4)
Fair value of plan assets at end of year	$ 39.8

Retirement and Postretiremen_13

Retirement and Postretirement Plans - Benefit Payments (Details) $ in Millions	Dec. 31, 2023 USD ($)
Pension
Benefit Payments:
2024	$ 73.1
2025	54.2
2026	56.4
2027	73.9
2028	59.9
2029-2033	268.9
Pension | Bargaining Plan | United States of America
Benefit Payments:
2024	39.4
2025	40.3
2026	43.1
2027	47.2
2028	46.7
2029-2033	206.9
Pension | Salaried Plan | United States of America
Benefit Payments:
2024	30.3
2025	10.5
2026	10.1
2027	9.8
2028	9.5
2029-2033	41.4
Pension | Supplemental Plan | United States of America
Benefit Payments:
2024	0.6
2025	0.6
2026	0.5
2027	13.8
2028	0.5
2029-2033	2
Pension | Pension Scheme | United Kingdom
Benefit Payments:
2024	2.8
2025	2.8
2026	2.7
2027	3.1
2028	3.2
2029-2033	18.6
Pension | Pension Plan | Mexico
Benefit Payments:
2027	0
Postretirement
Benefit Payments:
2024	9.7
2025	8.9
2026	8.3
2027	7.9
2028	7.5
2029-2033	$ 33.1

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details)				12 Months Ended
	Dec. 15, 2023	May 05, 2021 shares	May 06, 2020 USD ($) shares	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense | $				$ 11,500,000	$ 8,800,000	$ 7,300,000
Future stock-based compensation expense | $				$ 19,900,000
Future stock-based compensation expense, period of recognition				2 years 4 months 24 days
Time-Based Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting rights description				These restricted stock units do not have any performance conditions for vesting.
Performance-Based Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting rights description				The overall vesting period is generally three years, with relative total shareholder return measured for the one, two and three-year periods creating effectively a “nested” 1-year, 2-year, and 3-year performance period.
Vesting period				3 years
Number of trading days to calculate average closing stock price				20 days
Maximum [Member] | Performance-Based Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting Percentage	200%			200%
Minimum [Member] | Performance-Based Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting Percentage	0%			0%
Equity and incentive compensation 2020 plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate share limit ratio			1
Stock-based compensation, extended-term plan		May 05, 2031
Shares available for grant (in shares)			2,000,000
Shares available for grant (in shares)		2,000,000
Equity and incentive compensation 2020 plan | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)		2,000,000	2,000,000
Share-based compensation, full value award limit		1,800,000
Equity and incentive compensation 2020 plan | Non-employee Director | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation, maximum grant value | $			$ 500,000
Transformation Incentive Grant Program Activity
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of trading days to calculate average closing stock price	20 days
Number of consecutive trading days	20 days

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Number of Shares
Beginning balance (in shares)	1,119,523
Granted (in shares)	0	0	0
Exercised (in shares)	(291,928)
Canceled, forfeited or expired (in shares)	(206,245)
Ending balance (in shares)	621,350	1,119,523
Options expected to vest, number of shares (in shares)	66,360
Options exercisable, number of shares (in shares)	554,990
Weighted Average Exercise Price
Beginning balance (in USD per share)	$ 18.85
Granted (in USD per share)	0
Exercised (in USD per share)	10.11
Canceled, forfeited or expired (in USD per share)	33.93
Ending balance (in USD per share)	17.95	$ 18.85
Options expected to vest, weighted average exercise price (in USD per share)	5.26
Options exercisable, weighted average exercise price (in USD per share)	$ 19.47
Additional Information
Outstanding, weighted average remaining contractual term	3 years 6 months
Options expected to vest, weighted average remaining contractual term	6 years 2 months 12 days
Options exercisable, weighted average remaining contractual term	3 years 1 month 6 days
Outstanding, aggregate intrinsic value	$ 5.6
Options expected to vest, aggregate intrinsic value	1.2
Options exercisable, aggregate intrinsic value	$ 4.4

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Time-Based Restricted Stock Unit Activity (Details) - Time-Based Restricted Stock Units	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Number of Shares
Beginning balance (in shares) | shares	1,546,002
Granted (in shares) | shares	385,959
Vested (in shares) | shares	(302,935)
Canceled, forfeited or expired (in shares) | shares	(9,307)
Ending balance (in shares) | shares	1,619,719
Weighted Average Grant Date Fair Value
Beginning balance (in USD per share) | $ / shares	$ 9.29
Granted (in USD per share) | $ / shares	18.52
Vested (in USD per share) | $ / shares	11.41
Canceled, forfeited or expired (in USD per share) | $ / shares	18.19
Ending balance (in USD per share) | $ / shares	$ 11.99

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Performance-Based Restricted Stock Unit Activity (Details) - Performance-Based Restricted Stock Units	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Number of Shares
Beginning balance (in shares) | shares	968,415
Granted (in shares) | shares	211,639
Vested (in shares) | shares	(167,694)
Canceled, forfeited or expired (in shares) | shares	2,298
Ending balance (in shares) | shares	1,014,658
Weighted Average Grant Date Fair Value
Beginning balance (in USD per share) | $ / shares	$ 10.21
Granted (in USD per share) | $ / shares	23.13
Vested (in USD per share) | $ / shares	4.98
Canceled, forfeited or expired (in USD per share) | $ / shares	23.44
Ending balance (in USD per share) | $ / shares	$ 13.76

Stock-Based Compensation - Sc_3

Stock-Based Compensation - Schedule of Transformation Incentive Grant Program Activity (Details)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Transformation Incentive Grant Program Activity
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares) | shares	0
Canceled, forfeited or expired (in shares) | shares	0
Ending balance (in shares) | shares	350,000
Weighted Average Grant Date Fair Value
Beginning balance (in USD per share) | $ / shares	$ 0
Canceled, forfeited or expired (in USD per share) | $ / shares	0
Ending balance (in USD per share) | $ / shares	$ 22.46
Tier 1-2
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted (in shares) | shares	200,000
Weighted Average Grant Date Fair Value
Granted (in USD per share) | $ / shares	$ 22.22
Tier 3-4
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted (in shares) | shares	150,000
Weighted Average Grant Date Fair Value
Granted (in USD per share) | $ / shares	$ 22.78
Performance-Based Restricted Stock Units
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares) | shares	968,415
Granted (in shares) | shares	211,639
Canceled, forfeited or expired (in shares) | shares	(2,298)
Ending balance (in shares) | shares	1,014,658
Weighted Average Grant Date Fair Value
Beginning balance (in USD per share) | $ / shares	$ 10.21
Granted (in USD per share) | $ / shares	23.13
Canceled, forfeited or expired (in USD per share) | $ / shares	23.44
Ending balance (in USD per share) | $ / shares	$ 13.76

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 686.5	$ 664.6	$ 507.5
Other comprehensive income before reclassifications, before income tax	0	(1.7)
Amounts reclassified from accumulated other comprehensive income (loss), before income tax	(4.6)	(4.7)
Amounts deferred to accumulated other comprehensive income (loss), before income tax	2.3	0
Tax effect	0.2	0.4	0
Other comprehensive income (loss), net of tax	(2.3)	(6)	(19.7)
Ending balance	731.6	686.5	664.6
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(6.8)	(5.1)
Other comprehensive income before reclassifications, before income tax	0	(1.7)
Amounts reclassified from accumulated other comprehensive income (loss), before income tax	0.3	0
Amounts deferred to accumulated other comprehensive income (loss), before income tax	0	0
Tax effect	0	0
Other comprehensive income (loss), net of tax	0.3	(1.7)
Ending balance	(6.5)	(6.8)	(5.1)
Pension and Postretirement Liability Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	21.5	25.8
Other comprehensive income before reclassifications, before income tax	0	0
Amounts reclassified from accumulated other comprehensive income (loss), before income tax	(4.9)	(4.7)
Amounts deferred to accumulated other comprehensive income (loss), before income tax	2.3	0
Tax effect	0	0.4
Other comprehensive income (loss), net of tax	(2.6)	(4.3)
Ending balance	18.9	21.5	25.8
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	14.7	20.7	40.4
Other comprehensive income (loss), net of tax	(2.3)	(6)	(19.7)
Ending balance	$ 12.4	$ 14.7	$ 20.7

Contingencies - Narrative (Deta

Contingencies - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Loss Contingency Accrual, Disclosures [Abstract]
Contingency reserves	$ 1.1	$ 1.1

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Allowance for Uncollectible Accounts
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 1	$ 1.9	$ 1.3
Charged to Costs and Expenses	1.2	0	0.6
Deductions	(0.2)	(0.9)	0
Balance at End of Period	2	1	1.9
Allowance for Inventory Reserves
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	0.5	0.8	13.9
Charged to Costs and Expenses	1.1	0.5	2.8
Deductions	(0.9)	(0.8)	(15.9)
Balance at End of Period	0.7	0.5	0.8
Valuation Allowance on Deferred Tax Assets
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	13	15.5	47.7
Charged to Costs and Expenses	2.5	0	0
Charged to Other Accounts	0	0	4.8
Deductions	0	(2.5)	(37)
Balance at End of Period	$ 15.5	$ 13	$ 15.5

Subsequent Event - Narrative (D

Subsequent Event - Narrative (Details) $ in Millions	Feb. 27, 2024 USD ($)
Subsequent Event
Subsequent Event [Line Items]
Grant received	$ 99