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v3.23.3

Debt - Revolving Credit Facility Narrative (Details) |  | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | ---
Aug. 11, 2023 USD ($) | Sep. 30, 2023 USD ($) | Sep. 30, 2023 USD ($) segment | Sep. 30, 2022 USD ($) | Sep. 09, 2027 USD ($) | Dec. 31, 2022 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |
Debt issuance costs |  | $ 20,700,000 | $ 20,700,000 |  |  | $ 17,200,000
Pension Plans Defined Benefit |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Contributions by employer |  | 222,000,000 | 272,000,000 |  |  |
Foreign credit facilities |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Maximum borrowing capacity |  | 57,000,000 | 57,000,000 |  |  |
Short-term Debt |  | 11,200,000 | 11,200,000 |  |  | 19,400,000
Domestic Bank Group $600 million asset-based credit facility |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Bridge loan |  | 60,000,000 | 60,000,000 |  |  |
Amount utilized to support the issuance of letters of credit |  | 31,700,000 | 31,700,000 |  |  |
Average borrowings during period |  |  | 17,000,000 | $ 0 |  |
Short-term Debt |  | 0 | $ 0 |  |  | 0
Interest rate during period |  |  | 6.50% |  |  |
Domestic Bank Group $600 million asset-based credit facility | Revolving credit facility |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Maximum borrowing capacity |  | $ 600,000,000 | $ 600,000,000 |  |  |
Minimum fixed charge coverage ratio allowed in event of default |  | 1.00 | 1.00 |  |  |
Percentage of borrowing capacity unavailable due to fixed charge coverage ratio covenant |  | 10.00% | 10.00% |  |  |
Borrowing capacity unavailable due to fixed charge coverage ratio covenant, minimum |  | $ 60,000,000 | $ 60,000,000 |  |  |
Minimum required liquidity number of days prior to maturity of senior notes |  |  | 90 days |  |  |
Debt covenant, undrawn availability requirement, amount |  | $ 120,000,000 | $ 120,000,000 |  |  |
Debt covenant, undrawn availability requirement, percent of total available liquidity |  | 20.00% | 20.00% |  |  |
Domestic Bank Group $600 million asset-based credit facility | Revolving credit facility | Minimum | Base rate borrowings |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Variable interest rate (percentage) |  |  | 0.25% |  |  |
Domestic Bank Group $600 million asset-based credit facility | Revolving credit facility | Minimum | Secured Overnight Financing Rate (SOFR) |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Variable interest rate (percentage) |  |  | 1.25% |  |  |
Domestic Bank Group $600 million asset-based credit facility | Revolving credit facility | Maximum | Base rate borrowings |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Variable interest rate (percentage) |  |  | 0.75% |  |  |
Domestic Bank Group $600 million asset-based credit facility | Revolving credit facility | Maximum | Secured Overnight Financing Rate (SOFR) |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Variable interest rate (percentage) |  |  | 1.75% |  |  |
Domestic Bank Group $600 million asset-based credit facility | Letter of credit sub-facility |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Maximum borrowing capacity |  | $ 200,000,000 | $ 200,000,000 |  |  |
2027 Term Loan |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Outstanding borrowings |  | $ 200,000,000.0 | 200,000,000.0 |  |  | 200,000,000.0
Minimum prepayment increments allowed |  |  | $ 25,000,000 |  |  |
Interest rate |  | 4.21% | 4.21% |  |  |
2027 Term Loan | Interest Rate Swap |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Notional amount of derivative |  | $ 50,000,000 | $ 50,000,000 |  |  |
2027 Term Loan | Secured Overnight Financing Rate (SOFR) |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Variable interest rate (percentage) |  |  | 2.00% |  |  |
Allegheny Ludlum 6.95% Debentures due 2025 (a) |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Outstanding borrowings |  | $ 150,000,000.0 | $ 150,000,000.0 |  |  | $ 150,000,000.0
Interest rate |  | 6.95% | 6.95% |  |  | 6.95%
ATI 2030 Notes |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Outstanding borrowings |  | $ 425,000,000.0 | $ 425,000,000.0 |  |  | $ 0
Interest rate |  | 7.25% | 7.25% |  |  |
Debt issuance costs | $ 6,200,000 |  |  |  |  |
Debt instrument, amortization period |  |  | 7 years |  |  |
Debt instrument, redemption price, percentage |  |  | 101.00% |  |  |
Proceeds from Debt, Net of Issuance Costs | $ 418,800,000 |  |  |  |  |
ATI 2030 Notes | Minimum |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debt Instrument, Notice Period Required for Redemption | segment |  |  | 15 |  |  |
ATI 2030 Notes | Maximum |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debt Instrument, Notice Period Required for Redemption | segment |  |  | 60 |  |  |
Forecast | Domestic Bank Group $600 million asset-based credit facility | Revolving credit facility |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Line of credit facility, increase to maximum borrowing capacity |  |  |  |  | $ 300,000,000 |

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- Definition Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -SubTopic 10 -Topic 210 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481139/470-20-50-4 + Details
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- Definition Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482925/835-30-45-3 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1D -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481139/470-20-50-1D + Details
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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -SubTopic 10 -Topic 210 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)(a)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1 + Details
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