Indebtedness - Senior Debt Notes - Additional Information (Detail) $ in Thousands, NOK in Millions					1 Months Ended					3 Months Ended		12 Months Ended
		Nov. 15, 2013 USD ($)	Sep. 30, 2013 USD ($)	Aug. 15, 2011 USD ($)	May. 27, 2015 USD ($)	Mar. 31, 2015 USD ($)	Jan. 31, 2014 USD ($)	May. 31, 2012 NOK	Jul. 31, 2003 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2014 NOK	Mar. 31, 2016 USD ($) Trom	Mar. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)	Mar. 31, 2011 USD ($)	Mar. 31, 2016 NOK Trom	Jan. 31, 2014 NOK
Debt [Line Items]
Debt instrument outstanding amount						$ 1,534,476						$ 2,052,270	$ 1,534,476
Loss on early extinguishment of debt														$ (4,144)
Troms Offshore Supply AS
Debt [Line Items]
Number of Troms Offshore Debt tranches | Trom												4				4
Notes Due April 2027 | Troms Offshore Supply AS
Debt [Line Items]
Debt instrument maturity, month and year					2027-04
Debt instruments face amount					$ 31,300
Semi-annual principal payments					$ 1,300
Debt instrument bearing floating interest rate					2.92%
Indebtedness rate					1.30%
Total capitalization rate					4.22%
Debt instrument outstanding amount	[1]											$ 30,033
Notes Due January 2027 | Troms Offshore Supply AS
Debt [Line Items]
Debt instrument maturity, month and year						2027-01
Debt instruments face amount						$ 29,500							$ 29,500
Semi-annual principal payments						$ 1,200
Debt instrument bearing floating interest rate						2.91%							2.91%
Indebtedness rate						1.30%
Total capitalization rate						4.21%							4.21%
Debt instrument outstanding amount	[1]					$ 29,488						27,030	$ 29,488
Notes Due January 2026 | Troms Offshore Supply AS
Debt [Line Items]
Debt instrument maturity, month and year							2026-01
Debt instruments face amount | NOK																	NOK 300.0
Semi-annual principal payments							$ 12,500
Indebtedness rate							1.50%
Total capitalization rate																	3.81%
Debt instrument outstanding amount												30,200				NOK 250.0
Notes Due May 2024 | Troms Offshore Supply AS
Debt [Line Items]
Debt instrument maturity, month and year								2024-05
Debt instruments face amount | NOK								NOK 204.4
Semi-annual principal payments | NOK								NOK 8.5
Indebtedness rate							1.50%
Total capitalization rate																	5.38%
Debt instrument outstanding amount												$ 17,500				NOK 144.8
Debt instrument bearing interest rate								6.38%									3.88%
Public bonds | Troms Offshore Supply AS
Debt [Line Items]
Debt extinguished amount										$ 82,100	NOK 500.0
Repayment of bond at average price as a percentage of par value										105.00%	105.00%
Loss on early extinguishment of debt										$ (4,100)	NOK (26.0)
Minimum
Debt [Line Items]
Interest coverage ratio												300.00%				300.00%
Minimum | Troms Offshore Supply AS
Debt [Line Items]
Interest coverage ratio												300.00%				300.00%
Minimum | Notes Due January 2026 | Troms Offshore Supply AS
Debt [Line Items]
Debt instrument bearing floating interest rate																	2.31%
Maximum
Debt [Line Items]
Consolidated debt to consolidated total capitalization, ratio												55.00%
Maximum | Troms Offshore Supply AS
Debt [Line Items]
Consolidated debt to consolidated total capitalization, ratio												55.00%
September 2013 Senior Unsecured Notes
Debt [Line Items]
Senior note issuable amount under purchase agreement			$ 500,000
Sale of debt outstanding		$ 200,000	$ 300,000									$ 500,000
September 2013 Senior Unsecured Notes | Minimum
Debt [Line Items]
Debt instrument maturity, in years												7 years
Interest coverage ratio												300.00%				300.00%
September 2013 Senior Unsecured Notes | Maximum
Debt [Line Items]
Debt instrument maturity, in years												12 years
Consolidated debt to consolidated total capitalization, ratio												55.00%
August 2011 Senior Unsecured Notes
Debt [Line Items]
Sale of debt outstanding				$ 165,000
August 2011 Senior Unsecured Notes | Minimum
Debt [Line Items]
Debt instrument maturity, in years												8 years
August 2011 Senior Unsecured Notes | Maximum
Debt [Line Items]
Debt instrument maturity, in years												10 years
Consolidated debt to consolidated total capitalization, ratio												55.00%
September 2010 Senior Unsecured Notes
Debt [Line Items]
Sale of debt outstanding															$ 425,000
After-tax loss relating to interest rate hedges												$ 1,500	1,800
Pre-tax loss relating to interest rate hedges												$ 2,400	$ 2,600
September 2010 Senior Unsecured Notes | Minimum
Debt [Line Items]
Debt instrument maturity, in years												5 years
September 2010 Senior Unsecured Notes | Maximum
Debt [Line Items]
Debt instrument maturity, in years												12 years
Consolidated debt to consolidated total capitalization, ratio												55.00%
July 2003 Senior Unsecured Notes
Debt [Line Items]
Sale of debt outstanding									$ 300,000
July 2003 Senior Unsecured Notes | Minimum
Debt [Line Items]
Debt instrument maturity, in years												7 years
July 2003 Senior Unsecured Notes | Maximum
Debt [Line Items]
Debt instrument maturity, in years												12 years
Consolidated debt to consolidated total capitalization, ratio												55.00%

[1] Note requires semi-annual principal payments.