Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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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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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

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The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

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Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Section 45
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Derivatives (Effects of Derivatives on Measures of Financial Performance) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2015	Dec. 31, 2014
Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	$ 0	$ (136)	$ 6,098	$ 5,745
Gains (Losses) Reclassified from Accumulated OCI into Income (Effective Portion)	0	397	9,575	2,643
Successor [Member] \| Coal [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	(408)
Coal derivative settlements, non-hedging	116
Successor [Member] \| Heating Oil-Diesel Purchases [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)	827
Successor [Member] \| Heating Oil-Fuel Surchages [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)	0
Successor [Member] \| Natural Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)	(91)
Successor [Member] \| Foreign Currency [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)	(9)
Predecessor [Member] \| Coal [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives		(1,662)	(3,883)	430
Coal derivative settlements, non-hedging		(476)	3,236	5,956
Predecessor [Member] \| Heating Oil-Diesel Purchases [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)		826	(8,294)	(7,848)
Predecessor [Member] \| Heating Oil-Fuel Surchages [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)		0		(405)
Predecessor [Member] \| Natural Gas [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)		(463)	878	0
Predecessor [Member] \| Foreign Currency [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)		(451)	(887)	0
Long [Member] \| Coal Contract [Member] \| Designated as Hedging Instrument [Member] \| Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	0	536	(6,718)	(5,097)
Gains (Losses) Reclassified from Accumulated OCI into Income (Effective Portion)	0	(1,237)	(9,060)	(2,693)
Short [Member] \| Coal Contract [Member] \| Designated as Hedging Instrument [Member] \| Sales Revenue, Net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	0	(672)	12,816	10,842
Gains (Losses) Reclassified from Accumulated OCI into Income (Effective Portion)	$ 0	$ 1,634	$ 18,635	$ 5,336