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Fair Value of Financial Instruments (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020 | Jul. 02, 2020
--- | --- | --- | ---
Allegheny Technologies, Convertible Senior Notes, 3.5%, Due 2025 [Member] | Convertible Debt [Member] |  |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |  |
Equity component of convertible debt | $ 0.0 | $ 46.8 | $ 51.4
Fair Value Measurements at Reporting Date Using Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |  |
Cash and cash equivalents | 687.7 | 645.9 |
Derivative financial instruments: Assets | 0.0 | 0.0 |
Derivative financial instruments: Liabilities | 0.0 | 0.0 |
Debt | 1,690.1 | 1,594.2 |
Fair Value Measurements at Reporting Date Using Significant Observable Inputs (Level 2) |  |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |  |
Cash and cash equivalents | 0.0 | 0.0 |
Derivative financial instruments: Assets | 7.6 | 4.8 |
Derivative financial instruments: Liabilities | 2.7 | 4.0 |
Debt | 313.1 | 253.5 |
Total Carrying Amount |  |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |  |
Cash and cash equivalents | 687.7 | 645.9 |
Derivative financial instruments: Assets | 7.6 | 4.8 |
Derivative financial instruments: Liabilities | 2.7 | 4.0 |
Debt | 1,863.7 | 1,629.1 |
Fair Value Measurements at Reporting Date Using Total Estimated Fair Value |  |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |  |
Cash and cash equivalents | 687.7 | 645.9 |
Derivative financial instruments: Assets | 7.6 | 4.8 |
Derivative financial instruments: Liabilities | 2.7 | 4.0 |
Debt | 2,003.2 | $ 1,847.7 |
Fair Value Measurements at Reporting Date Using Total Estimated Fair Value | Fair Value Measurements at Reporting Date Using Quoted Prices in Active Markets for Identical Assets (Level 1) | Allegheny Technologies, Convertible Senior Notes, 3.5%, Due 2025 [Member] | Convertible Debt [Member] |  |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |  |
Debt | $ 379.0 |  |

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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
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- Definition Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69C -URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495737-112612 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69B -URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495735-112612 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13433-108611 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 1D -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611 + Details
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- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 22 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226052-175313 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13433-108611 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details
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