Break Fees On Terminated Asset Sales

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Business Interruption Losses

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Derivative Instruments Not Designated as Hedging Instruments, Unrealized Gain (Loss), Net

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Fresh Start Adjustment, Fair Value Adjustment

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Fresh-Start Adjustment, Revaluation of Inventory

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Gain on formation of United Wambo JV

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Increase (Decrease) in Deferred Tax Asset Valuation Allowance and Amortization of Basis Difference Related to Equity Affiliates

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Mark-to-Market Adjustment on Pension and Postretirement Plans, Net

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Segment Reporting Information Adjusted Earning Before Interest Taxes Depreciation And Amortization.

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

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The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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The difference between the book value and the sale price of agreements to purchase or sell mineral resources, energy, and agricultural products at some future point. This element refers to the gain (loss) included in earnings and not to the cash proceeds.

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The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

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The net amount (to the extent disclosed within this portion of the income statement) by which an insurance settlement exceeds incremental costs incurred from the event causing an interruption of business, plus the insurance award for earnings lost from the event, such as a natural catastrophe, explosion or fire.

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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 after tax of income (loss) from continuing operations including portion attributable to the noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The amount recovered from insurance. These recoveries reduce costs and losses that are reported as a separate line item under operating expenses.

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The net amount of operating interest income (expense).

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

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Amount of expense related to other loss.

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Total amount of reorganization items.

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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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Segment and Geographic Information Reconciliation of Consolidated Income (Loss), Net of Income Taxes to Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended									9 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Apr. 01, 2017	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
(Loss) income from continuing operations, net of income taxes	$ 290.2	$ 74.3	$ (42.9)	$ (133.3)	$ (233.5)	$ (83.9)	$ (120.0)	$ (208.3)	$ 195.5	$ (713.1)	$ 188.3	$ (645.7)
Depreciation, depletion and amortization									119.9	521.6	601.0	679.0
Asset retirement obligation expenses									14.6	41.2	58.4	53.0
Gain on formation of United Wambo Joint Venture	48.1								0.0	0.0	48.1	0.0
Asset impairment	250.2	20.0							30.5	0.0	270.2	0.0
North Goonyella insurance recovery - equipment									0.0	0.0	91.1
Changes in deferred tax asset valuation allowance and reserves and amortization of basis difference related to equity affiliates									(5.2)	(17.3)	(18.8)	18.3
Interest expense									32.9	119.7	144.0	149.3
Loss on early debt extinguishment									0.0	20.9	0.2	2.0
Interest income	(4.5)	$ (7.0)	$ (7.2)	(8.3)	(9.3)	$ (10.1)	$ (7.0)	(7.2)	(2.7)	(5.6)	(27.0)	(33.6)
Net mark-to-market adjustment on actuarially determined liabilities	$ 67.4				$ 125.5				0.0	(45.2)	67.4	(125.5)
Reorganization items, net								$ 12.8	627.2	0.0	0.0	(12.8)
Break fees related to terminated asset sales									0.0	(28.0)	0.0	0.0
Unrealized (gains) losses on economic hedges									(16.6)	23.0	(42.2)	18.3
Unrealized (gains) losses on non-coal trading derivative contracts									0.0	1.5	(1.2)	(0.7)
Fresh start coal inventory revaluation									0.0	67.3	0.0	0.0
Fresh start take-or-pay contract-based intangible recognition									0.0	(22.5)	(16.6)	(26.7)
Income tax provision (benefit)									(263.8)	(161.0)	46.0	18.4
Total Adjusted EBITDA									341.3	1,145.3	837.1	1,379.3
Insurance Recoveries				$ 125.0					0.0	0.0	125.0	0.0
Payments to Acquire Property, Plant, and Equipment									32.8	166.6	285.4	301.0
North Goonyella Mine
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Insurance Recoveries											125.0
Provision for equipment loss excluded from EBITDA											24.7	66.4
Business Interruption Losses											33.9
Springfield Reclamation Liability
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Gain on disposals									0.0	(31.2)	0.0	0.0
Burton Mine
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Gain on disposals									$ 0.0	$ (52.2)	$ 0.0	$ 0.0