Stockholders' Equity - Reclassifications From Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	4 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2017	Aug. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period, net of tax	$ 0
Predecessor
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period, net of tax		$ 1,008	$ (1,823)
Prior service cost
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	0
Prior service cost | Predecessor
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		(133)	(200)
Actuarial (loss) gain
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	0
Actuarial (loss) gain | Predecessor
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		1,141	(1,623)
Defined Benefit Pension and Postretirement Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	0
Tax effect	0
Total reclassifications for the period, net of tax	$ 0
Defined Benefit Pension and Postretirement Items | Predecessor
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		1,008	(1,823)
Tax effect		0	0
Total reclassifications for the period, net of tax		$ 1,008	$ (1,823)