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Commitments and Contingencies - Legal Contingencies (Details) - USD ($)		1 Months Ended	12 Months Ended
	Aug. 18, 2017	Sep. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2013
Loss Contingencies [Line Items]
Gain recognized			$ 0	$ 0	$ 5,500,000
Ravenswood Retiree Medical Benefits Changes [Member]
Loss Contingencies [Line Items]
Litigation settlement amount	$ 23,000,000.0
Litigation settlement period			10 years
Ravenswood retiree legal settlement		$ 5,000,000.0
Gain recognized		5,500,000
Loss contingency accrual		$ 12,500,000
Other liabilities, current			$ 2,000,000.0
Other liabilities			8,700,000
Litigation settlement, annual installment			$ 2,000,000.0
Litigation settlement installment period			9 years
PBGC Agreement [Member]
Loss Contingencies [Line Items]
Required pension contributions above minimum						$ 17,400,000
Pension contributions			$ 0	$ 0	$ 0
Pension contributions above minimum remaining			$ 9,600,000

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- Definition

Litigation Settlement, Annual Installment

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Pursuant to the terms of the settlement agreement with the Pension Benefit Guaranty Corporation, this amount represents the remaining additional contributions (above any minimum required contributions) to our defined benefit pension plans.

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Pursuant to the terms of the settlement agreement with the Pension Benefit Guaranty Corporation, we will make additional contributions (above any minimum required contributions) to our defined benefit pension plans.

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- Definition

Amount of gain (loss) recognized in settlement of litigation and insurance claims. Excludes claims within an insurance entity's normal claims settlement process.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
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Amount awarded to other party in judgment or settlement of litigation.

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Amount of loss contingency liability.

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The amount of cash paid for the settlement of litigation or for other legal issues during the period.

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Amount of cash outflow for pension benefit. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree. Excludes other postretirement benefit.

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