Commitments and Contingencies - Additional Information (Detail) $ in Thousands		1 Months Ended							3 Months Ended
		Jul. 31, 2016 USD ($)	Jan. 31, 2016 USD ($)	Sep. 30, 2015 USD ($) Vessel T hp	Jul. 31, 2015 USD ($)	Jun. 30, 2015 USD ($) Vessel T hp	May 31, 2015 USD ($)	Apr. 30, 2015 Vessel T	Jun. 30, 2016 USD ($) Vessel T		Mar. 31, 2016 USD ($)	Jun. 30, 2015 USD ($) T hp	Dec. 31, 2015 USD ($)
Significant Purchase and Supply Commitment [Line Items]
Number of vessels under construction | Vessel				9
Refunds from cancelled vessel construction contracts			$ 12,000						$ 11,515			$ 24,190
Accrued interest owing on the returned installments				$ 3,700
Refunds from cancelled vessel construction contracts				31,000					17,000
Relieved obligation				$ 75,000
Deferred final installment of vessel construction contracts									$ 5,000
Fast, Crew/Supply Boat
Significant Purchase and Supply Commitment [Line Items]
Number of vessels under construction | Vessel									1
Impairment charge on amounts not recoverable									$ 2,400
Insurance coverage for the progress payments made on the vessel by the third party credit support									90.00%
Insurance coverage by the third party credit support for the carrying value of the accumulated costs									$ 2,400
Fast, Crew/Supply Boat | Reclassification of Construction in Progress to Other Non-Current Assets
Significant Purchase and Supply Commitment [Line Items]
Committed and invested amount, remaining									5,600
Vessel Commitments
Significant Purchase and Supply Commitment [Line Items]
Remaining Balance, commitments	[1]								$ 57,919
Number of Vessels, commitments | Vessel	[1]								4
Unfunded capital commitment, net of expected refunds									$ 41,000
Expected refunds from shipyards									$ 17,000
Deepwater PSVs
Significant Purchase and Supply Commitment [Line Items]
Significant commitment, new construction deadweight tons capacity range, low | T									4,700
Significant commitment, new construction deadweight tons capacity range, high | T									5,400
Significant commitment, new construction final delivery date									2017-05
Number of vessels under construction | Vessel				6				2	4	[2]
Significant commitment, new construction deadweight tons capacity | T				4,700				3,800
Impairment charge on amounts not recoverable											$ 1,900
Refunds from cancelled vessel construction contracts									$ 19,100
Net payment to company on vessel construction									14,100
Aggregate installment payment							$ 5,400		123,696	[2]
Obligation to be relieved							21,700
Aggregate installment payment payment with interest							$ 11,900
Shipyard returned to the company									11,500
Shipyard owed amount									11,700
Foreign taxes on interest									200
Remaining installment obligation held									$ 250
Extended option period for vessels									Dec. 31, 2016
Vessels Under Construction
Significant Purchase and Supply Commitment [Line Items]
Number of vessels under construction | Vessel						6
Significant commitment, new construction brake horsepower | hp						7,145						7,145
Significant commitment, new construction deadweight tons capacity | T						4,700						4,700
Refunds from cancelled vessel construction contracts					$ 12,000	$ 24,000			$ 36,000
Accrued interest owing on the returned installments									3,500
Impairment charge on amounts not recoverable												$ 800
Vessels Under Construction | Shipyard Credit
Significant Purchase and Supply Commitment [Line Items]
Offset against other payment													$ 3,500
Towing Supply Vessels
Significant Purchase and Supply Commitment [Line Items]
Number of vessels under construction | Vessel				3
Significant commitment, new construction brake horsepower | hp				7,145
First Deepwater PSVs
Significant Purchase and Supply Commitment [Line Items]
Deferred final installment of vessel construction contracts									$ 2,500
Second Deepwater PSVs | Subsequent Event
Significant Purchase and Supply Commitment [Line Items]
Deferred final installment of vessel construction contracts		$ 2,500

[1] The company is entitled to receive a refund of prior shipyard payments totaling approximately $17 million which would reduce the remaining balance of vessel commitments. See further discussion below.

[2] Six additional option vessels and a fast supply boat are not included in the table above.