Commitments and Contingencies - Additional Information (Detail) $ in Thousands		1 Months Ended				3 Months Ended	9 Months Ended
		Jan. 31, 2016 USD ($)	Jul. 31, 2015 USD ($)	Jun. 30, 2015 Vessel	May. 31, 2015 USD ($) Vessel	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) Vessel hp T		Sep. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)
Significant Purchase and Supply Commitment [Line Items]
Number of Vessels, commitments | Vessel							9
Refunds from cancelled vessel construction contracts							$ 36,190
Accrued interest owing on the returned installments									$ 3,700
Refunds from cancelled vessel construction contracts							$ 43,000		31,000
Relieved obligation									$ 75,000
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
Subsequent Event
Significant Purchase and Supply Commitment [Line Items]
Refunds from cancelled vessel construction contracts		$ 12,000
Deepwater PSVs
Significant Purchase and Supply Commitment [Line Items]
Significant commitment, new construction deadweight tons capacity range, low | T							4,200
Significant commitment, new construction deadweight tons capacity range, high | T							6,000
Significant commitment, new construction final delivery date							May 2017
Number of vessels under construction | Vessel					2		8	[1]
Aggregate installment payment					$ 5,400		$ 231,256	[1]		$ 1,000
Significant commitment, new construction delivery date					Jun. 30, 2016
Obligation to be relieved					$ 21,700
Aggregate installment payment payment with interest					$ 12,000
Towing Supply Vessels
Significant Purchase and Supply Commitment [Line Items]
Significant commitment, new construction brake horsepower | hp							7,145
Number of vessels under construction | Vessel	[1]						1
Aggregate installment payment	[1]						$ 13,580
Vessel Commitments
Significant Purchase and Supply Commitment [Line Items]
Unfunded capital commitment	[1],[2]						$ 107,190
Number of Vessels, commitments | Vessel	[1],[2]						9
Unfunded capital commitment, net of expected refunds							$ 64,000
Expected refunds from shipyards							43,000
Vessels Under Construction
Significant Purchase and Supply Commitment [Line Items]
Number of vessels under construction | Vessel				6
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

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

[2] The company is entitled to receive a refund of prior shipyard payments totaling approximately $43 million (of which $12 million was received in January 2016) which would offset the remaining balance of vessel commitments. See further discussion below.