Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Inventories	$ 128,960	$ 113,462
Allowance for slow-moving and obsolete inventories	300	0
Successor
Property, Plant and Equipment [Line Items]
Coal	54,692
Repair parts and supplies	74,268
Inventories	$ 128,960
Predecessor
Property, Plant and Equipment [Line Items]
Coal		37,268
Repair parts and supplies		76,194
Inventories		$ 113,462