Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets
Other current assets		$ 39,866
Current liabilities
Current maturities of debt		5,042,353
Predecessor [Member]
Current assets
Cash and cash equivalents		450,781
Short term investments		200,192
Restricted cash		97,542
Trade accounts receivable (net of allowance for doubtful accounts of $0.0 million and $7.8 million, respectively)		117,405
Other receivables		18,362
Inventories		196,720
Prepaid royalties		10,022
Deferred income taxes		0
Coal derivative assets		8,035
Other current assets		39,866
Total current assets		1,138,925
Property, plant and equipment
Coal lands and mineral rights		3,713,639
Plant and equipment		2,359,674
Deferred mine development		553,286
Property, plant and equipment, gross		6,626,599
Less accumulated depreciation, depletion and amortization		(3,007,570)
Property, plant and equipment, net		3,619,029
Other assets
Prepaid royalties		23,671
Equity investments		201,877
Other noncurrent assets		58,379
Total other assets		283,927
Total assets		5,041,881
Current liabilities
Accounts payable		128,131
Accrued expenses and other current liabilities		329,450
Current maturities of debt		5,042,353
Total current liabilities		5,499,934
Long-term debt		30,953
Asset retirement obligations		396,659
Accrued pension benefits		27,373
Accrued postretirement benefits other than pension		99,810
Accrued workers’ compensation		112,270
Other noncurrent liabilities		119,171
Total liabilities		6,286,170
Stockholders' equity (deficit)
Common stock		2,145
Paid-in capital		3,054,211
Treasury stock, at cost		(53,863)
Retained earnings (accumulated deficit)		(4,244,967)
Accumulated other comprehensive income (loss)		(1,815)
Total stockholders’ equity (deficit)		(1,244,289)
Total liabilities and stockholders’ equity (deficit)		$ 5,041,881
Successor [Member]
Current assets
Cash and cash equivalents	$ 305,372
Short term investments	88,072
Restricted cash	71,050
Trade accounts receivable (net of allowance for doubtful accounts of $0.0 million and $7.8 million, respectively)	184,483
Other receivables	19,877
Inventories	113,462
Prepaid royalties	2,281
Deferred income taxes	0
Coal derivative assets	262
Other current assets	93,763
Total current assets	878,622
Property, plant and equipment
Coal lands and mineral rights	387,591
Plant and equipment	418,182
Deferred mine development	280,323
Property, plant and equipment, gross	1,086,096
Less accumulated depreciation, depletion and amortization	(32,493)
Property, plant and equipment, net	1,053,603
Other assets
Prepaid royalties	0
Equity investments	96,074
Other noncurrent assets	108,298
Total other assets	204,372
Total assets	2,136,597
Current liabilities
Accounts payable	95,953
Accrued expenses and other current liabilities	205,240
Current maturities of debt	11,038
Total current liabilities	312,231
Long-term debt	351,841
Asset retirement obligations	337,227
Accrued pension benefits	38,884
Accrued postretirement benefits other than pension	101,445
Accrued workers’ compensation	184,568
Other noncurrent liabilities	63,824
Total liabilities	1,390,020
Stockholders' equity (deficit)
Common stock	250
Paid-in capital	688,424
Treasury stock, at cost	0
Retained earnings (accumulated deficit)	33,449
Accumulated other comprehensive income (loss)	24,454
Total stockholders’ equity (deficit)	746,577
Total liabilities and stockholders’ equity (deficit)	$ 2,136,597