Schedule of Amounts Due to Affiliate (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Schedule Of Equity Method Investments [Line Items]
Begining balance	$ 34,972
Ending balance	39,060
Sonatide Marine, Ltd.
Schedule Of Equity Method Investments [Line Items]
Begining balance	29,347
Plus additional commissions payable to Sonatide	2,828
Plus amounts paid by Sonatide on behalf of the company	5,093
Less commissions paid to Sonatide during the period	(5,961)
Less amounts used to offset Due from Sonatide obligations	(7,982)	[1]
Other	4,125
Ending balance	$ 27,450

[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.