Schedule of Vessel Commitments (Detail) $ in Thousands	3 Months Ended
	Jun. 30, 2017 USD ($) Vessel
Vessel Commitments
Significant Purchase and Supply Commitment [Line Items]
Number of Vessels, commitments | Vessel	1
Total cost, commitments	$ 53,639
Invested, commitments	47,452
Remaining Balance, commitments	$ 6,187
Deepwater PSV
Significant Purchase and Supply Commitment [Line Items]
Number of Vessels, commitments | Vessel	1
Remaining Balance, commitments	$ 6,200
Number of vessels under construction | Vessel	1	[1]
Total cost, under construction	$ 53,639	[1]
Invested, under construction	47,452	[1]
Remaining Balance, under construction	$ 6,187	[1]

[1] Two remaining option vessels, a vessel rejected at the time of delivery and a fast supply boat are not included in the table above.