Employee Benefit Plans - Schedule of Net Benefit Costs (Details) - Pension and Other Postretirement Plans, Defined Benefit - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 117		$ 234
Interest cost	1,225		2,450
Expected return on assets	(1,971)		(3,942)
Amortization of prior service cost	0		0
Amortization of actuarial loss	0		0
Net periodic pension and postretirement benefit gain	(629)		(1,258)
Contributions paid	$ 0		$ 0
Predecessor
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		$ 105		$ 211
Interest cost		1,211		2,421
Expected return on assets		(2,035)		(4,069)
Amortization of prior service cost		50		100
Amortization of actuarial loss		164		328
Net periodic pension and postretirement benefit gain		(505)		(1,009)
Contributions paid		$ 0		$ 356