Quarterly Selected Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								6 Months Ended	9 Months Ended	12 Months Ended
	Oct. 01, 2016	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2015	Oct. 01, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Asset impairment and mine closure costs						$ 488,900	$ 2,100,000	$ 19,100		$ 2,600,000
Predecessor [Member]
Class of Stock [Line Items]
Revenues			$ 550,305	$ 420,298	$ 428,106	563,249	688,544	644,462	$ 677,005		$ 1,398,709	$ 2,573,260	$ 2,937,119
Gross profit (loss)			31,042	(56,469)	(53,325)	(44,964)	47,275	(16,507)	14,256
Asset impairment and mine closure costs			46	43,701	85,520	488,865	2,120,292	19,146	0		129,267	2,628,303	24,113
Income (loss) from operations			11,795	(110,521)	(158,412)	(539,033)	(2,236,772)	(69,546)	(19,712)		(257,138)	(2,865,063)	(149,531)
Reorganization items, net	$ 1,676,091		(20,904)	(21,271)	(3,875)						1,630,041	0	0
Net income (loss)	$ 1,676,091		$ (51,421)	$ (175,887)	$ (206,702)	$ (632,368)	$ (1,999,476)	$ (168,103)	$ (113,195)		$ 1,242,081	$ (2,913,142)	$ (558,353)
Diluted earnings per common share (in dollars per share)	$ 78.66		$ (2.41)	$ (8.26)	$ (9.71)	$ (29.70)	$ (93.91)	$ (7.93)	$ (5.32)		$ 58.28	$ (136.86)	$ (26.31)
Successor [Member]
Class of Stock [Line Items]
Revenues		$ 575,688
Gross profit (loss)		64,458
Asset impairment and mine closure costs		0
Income (loss) from operations		46,118
Reorganization items, net		(759)
Net income (loss)		$ 33,449
Diluted earnings per common share (in dollars per share)		$ 1.31