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, 2018	Dec. 31, 2017
SUCCESSOR
Defined Contribution Plan Disclosure [Line Items]
401(k) Plan expense		$ 3,554	$ 5,884	$ 5,386
SUCCESSOR | Support Group
Defined Contribution Plan Disclosure [Line Items]
401(k) Plan expense		$ 554	$ 1,066	$ 888
PREDECESSOR
Defined Contribution Plan Disclosure [Line Items]
401(k) Plan expense	$ 1,593
PREDECESSOR | Support Group
Defined Contribution Plan Disclosure [Line Items]
401(k) Plan expense	$ 319