Taxes (Schedule of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 1,022,000	$ 1,135,000
Predecessor [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards		1,086,332
Alternative minimum tax credit carryforwards		120,994
Investment in tax partnerships & corporations		0
Reclamation and mine closure		121,276
Goodwill		38,671
Workers’ compensation		42,835
Share based compensation		22,612
Sales contracts		17,466
Retiree benefit plans		16,996
Advance royalties		18,751
Losses from disposed operations resulting from Patriot Coal bankruptcy		39,287
Other, primarily accrued liabilities		45,303
Gross deferred tax assets		1,570,523
Valuation allowance		(1,135,399)
Total deferred tax assets		435,124
Plant and equipment		389,169
Deferred development		41,047
Sales contracts		0
Other		4,706
Total deferred tax liabilities		434,922
Net deferred (asset) liability		$ (202)
Successor [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	376,293
Alternative minimum tax credit carryforwards	22,798
Investment in tax partnerships & corporations	604,914
Reclamation and mine closure	0
Goodwill	5,135
Workers’ compensation	0
Share based compensation	0
Sales contracts	0
Retiree benefit plans	4,013
Advance royalties	0
Losses from disposed operations resulting from Patriot Coal bankruptcy	0
Other, primarily accrued liabilities	30,103
Gross deferred tax assets	1,043,256
Valuation allowance	(1,021,553)
Total deferred tax assets	21,703
Plant and equipment	7,332
Deferred development	0
Sales contracts	12,658
Other	1,600
Total deferred tax liabilities	21,590
Net deferred (asset) liability	$ (113)