Workers' Compensation Expense (Occupational Disease Costs Activity and Assumptions) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Oct. 01, 2016	Dec. 31, 2015	Dec. 31, 2014
Self Insurance Reserve [Roll Forward]
Curtailments		$ 3,600
Successor [Member]
Self Insurance Reserve [Roll Forward]
Service cost	$ 1,583
Interest cost	1,126
Predecessor [Member]
Self Insurance Reserve [Roll Forward]
Service cost			$ 3,465	$ 4,282	$ 1,734
Interest cost			3,184	3,944	2,914
Occupational Disease [Member] | Successor [Member]
Self Insurance Reserve [Roll Forward]
Service cost	1,583
Interest cost	1,126
Curtailments	0
Actuarial (gain) loss	(9,675)
Benefit and administrative payments	(1,585)
Fresh start accounting adjustment	0
End of period	$ 111,159
Discount rate (percent)	4.31%
Occupational Disease [Member] | Predecessor [Member]
Self Insurance Reserve [Roll Forward]
Beginning of period	$ 119,710	$ 90,836	90,836	72,749
Service cost			3,465	4,282
Interest cost			3,184	3,944
Curtailments			4,156
Actuarial (gain) loss			0	14,284
Benefit and administrative payments			(3,728)	(4,423)
Fresh start accounting adjustment			21,797	0
End of period			$ 119,710	$ 90,836	$ 72,749
Discount rate (percent)			3.80%	4.76%