Pension Plan and Employee Benefits, 401 (K) Plans (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 12, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2015
Successor [Member]
401(k) Plan [Abstract]
401 (k) Plan expense		$ 3,554	$ 5,386
Predecessor [Member]
401(k) Plan [Abstract]
401 (k) Plan expense	$ 1,593			$ 5,029
Other Subsidiaries [Member] | Successor [Member]
401(k) Plan [Abstract]
401 (k) Plan expense		$ 554	$ 888
Other Subsidiaries [Member] | Predecessor [Member]
401(k) Plan [Abstract]
401 (k) Plan expense	$ 319			$ 944