Amounts Charged to Expense Related to Defined Contribution Plans (Detail) - USD ($) $ in Thousands	4 Months Ended	5 Months Ended	12 Months Ended
	Jul. 31, 2017	Dec. 31, 2017	Dec. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plans expense, net of forfeitures			$ 3
Defined contribution plans forfeitures			$ 152
Defined Contribution Savings Plan 401k
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plans expense, net of forfeitures		$ 854
Defined contribution plans forfeitures		$ 83
Defined Contribution Savings Plan 401k | Predecessor
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plans expense, net of forfeitures	$ 871			$ 2,660
Defined contribution plans forfeitures	$ 79			$ 149