Schedule of Amounts Due from Affiliate (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Schedule Of Equity Method Investments [Line Items]
Begining balance	$ 132,951
Ending balance	121,959
Sonatide Marine, Ltd.
Schedule Of Equity Method Investments [Line Items]
Begining balance	109,176
Revenue earned by the company through Sonatide	29,650
Less amounts received from Sonatide	(35,699)
Less amounts used to offset Due to Sonatide obligations	(7,982)	[1]
Other	(1,005)
Ending balance	$ 94,140

[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.