Schedule of Amounts Due to Affiliate (Detail) - USD ($) $ in Thousands		4 Months Ended	5 Months Ended	12 Months Ended
		Jul. 31, 2017	Dec. 31, 2017	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Begining balance				$ 99,448
Ending balance			$ 99,448	34,972
Sonatide Marine, Ltd.
Schedule of Equity Method Investments [Line Items]
Begining balance			123,899	99,448
Plus commissions payable to Sonatide			3,928	5,502
Plus amounts paid by Sonatide on behalf of the company			12,044	14,778
Less commissions paid to Sonatide			(5,023)	(13,906)
Less amounts used to offset Due from Sonatide obligations	[1]		(33,607)	(78,993)
Other			(1,793)	2,518
Ending balance		$ 123,899	99,448	$ 29,347
Predecessor | Sonatide Marine, Ltd.
Schedule of Equity Method Investments [Line Items]
Begining balance		132,857	$ 123,899
Plus commissions payable to Sonatide		3,330
Plus amounts paid by Sonatide on behalf of the company		9,458
Less amounts used to offset Due from Sonatide obligations	[1]	(21,453)
Other		(293)
Ending balance		$ 123,899

[1] We reduced the respective due from affiliates and due to affiliates balances each period through netting transactions based on agreement with the joint venture.