Deconsolidation, Gain (Loss), Amount, Net of tax

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Disposal Group, Not Discontinued Operation, Gain (Loss) On Disposal, Net Of Tax

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Gain (Loss) On Disposition Of Oil And Gas And Timber Property, Net Of Tax

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Inventory, Net Realizable Value Reserve, Period Charge

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Other Asset Impairment Charges And Due From Affiliates, Allowance For Credit Loss

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Other Asset Impairment Charges And Due From Affiliates, Allowance For Credit Loss, Net Of Tax

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- Definition

Restructuring And Other Charges, Net Of Tax

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Restructuring and other charges

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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.

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Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

Amount of gain (loss) from deconsolidation of subsidiary and derecognition of group of assets constituting transfer of business or nonprofit activity, excluding conveyance of oil and gas mineral rights and transfer of good or service in contract with customer.

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Amount before tax of gain (loss) recognized on the sale or disposal of a disposal group. Excludes discontinued operations.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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- Definition

The difference between the reacquisition price and the net carrying amount of the extinguished debt recognized currently as a component of income in the period of extinguishment, net of tax.

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- Definition

Amount of gain (loss) on sale or disposal of oil and gas property or timber property.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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- Definition

Number of new stock issued during the period.

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

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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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Selected Quarterly Financial Data (Unaudited) - Narrative (Details) - USD ($) shares in Millions, $ in Millions		3 Months Ended				12 Months Ended
	Nov. 07, 2017	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unusual Or Infrequent Item [Line Items]
Gain (Loss) on Disposition of Oil and Gas and Timber Property			$ 62.4	$ 29.3		$ 91.7
Gain (Loss) On Disposition Of Oil And Gas And Timber Property, Net Of Tax			60.5	27.3
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal						(1.8)	$ 0.0	$ 0.0
Restructuring and other charges		$ (4.5)				(4.5)	0.0	0.0
Restructuring And Other Charges, Net Of Tax		(4.3)
Gain on joint venture deconsolidation					$ 15.9	0.0	15.9	0.0
Deconsolidation, Gain (Loss), Amount, Net of tax					$ 14.7
NRV charge						25.6	(27.9)	(54.0)
Impairment of goodwill						0.0	0.0	114.4
Debt extinguishment charge		(21.6)				(21.6)	0.0	(37.0)
Debt extinguishment charge, net of tax		(20.5)
Non-cash joint venture impairment charge		(11.4)				(11.4)	$ 0.0	$ 0.0
Non-cash joint venture impairment charge, net of tax		(10.8)
Valuation allowance decrease due to change in judgment on the realizability of deferred tax assets		$ 41.9				45.1
Shares issued	17
Allegheny Technologies $350 million 9.375% Senior Notes due 2019
Unusual Or Infrequent Item [Line Items]
Debt instrument carrying amount									$ 350.0
Debt Instrument, Interest Rate, Stated Percentage									9.375%
Allegheny & Tsingshan Stainless
Unusual Or Infrequent Item [Line Items]
Non-cash joint venture impairment charge						$ (11.4)
Equity method investment ownership percentage		50.00%				50.00%
Forged Products
Unusual Or Infrequent Item [Line Items]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal				(7.7)		$ (8.1)
Disposal Group, Not Discontinued Operation, Gain (Loss) On Disposal, Net Of Tax				$ (7.2)
Cast Products
Unusual Or Infrequent Item [Line Items]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			6.2			$ 6.2
Disposal Group, Not Discontinued Operation, Gain (Loss) On Disposal, Net Of Tax			$ 6.0
Tsingshan Group \| Allegheny & Tsingshan Stainless
Unusual Or Infrequent Item [Line Items]
Equity method investment ownership percentage		50.00%				50.00%