Schedule of Amounts Due to Affiliate (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($)
Schedule of Equity Method Investments [Line Items]
Beginning balance	$ 50,186
Ending balance	48,803
Sonatide Marine, Ltd.
Schedule of Equity Method Investments [Line Items]
Beginning balance	31,475
Plus additional commissions payable to Sonatide	2,265
Plus amounts paid by Sonatide on behalf of the company	4,843
Less amounts used to offset Due from Sonatide obligations	(8,145)	[1]
Other	(48)
Ending balance	$ 30,390

[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.