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Amount represents the upper future estimate of the Company's annual cash costs related to the Combined Benefit Fund.

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Combined Benefit Fund Liability

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Amount represents the lower future estimate of the Company's annual cash costs related to the Combined Benefit Fund.

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estimated fund onbligations

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Number of Buyers

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Number of Retirees

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Potential exposure from Patriot bankruptcy related to certain federal and state black lung occupational disease liabilities

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Amount before tax of income (loss) from a discontinued operation. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

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Aggregate carrying amount of the estimated litigation liability for known or estimated probable loss from litigation, which may include attorneys' fees and other litigation costs.

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Discontinued Operations - Patriot Related Matters (Details) $ in Millions		3 Months Ended		6 Months Ended
	Jan. 25, 2017 USD ($)	Jun. 30, 2019 USD ($) retirees	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) retirees	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Oct. 09, 2015 buyers	Dec. 31, 2007 USD ($)	Oct. 31, 2007 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Retirees \| retirees		0		0
Estimated fund obligation									$ 40.0
Amount contributed to the Combined Benefit Fund		$ 0.5	$ 0.5	$ 1.0	$ 1.1
CombinedBenefitFundLowerEstimate		1.0
CombinedBenefitFundFutureEstimate		2.0
Combined Benefit Fund Liability		15.7		15.7		$ 16.4
Combined benefit fund [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax		0.1	$ 0.1	0.3	$ 0.3
Patriot
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buyers \| buyers							2
Spinoff \| Patriot \| Black Lung Occupational Disease Liability
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Initially Determined Potential Exposure from Patriot Bankruptcy								$ 150.0
Potential Exposure from Patriot Bankruptcy		103.3		103.3		102.7
Spinoff \| UMWA 1974 Pension Plan (UMWA Plan) Litigation \| Patriot
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Settlement of claim, amount awarded to other party	$ 75.0
Litigation settlement, liability		$ 23.9		$ 23.9		$ 36.7