Summary of Norwegian Kroner (NOK) Denominated Borrowings Outstanding (Parenthetical) (Detail)		6 Months Ended
		Sep. 30, 2016	Mar. 31, 2016
January 2014 3.81% notes
Debt [Line Items]
Debt Instrument Maturity Period	[1]	January 2014
Debt instrument interest rate	[1]	3.81%	3.81%
January 2014 3.81% notes | Troms Offshore Supply AS
Debt [Line Items]
Debt instrument maturity, in years		12 years
May 2012 5.38% notes
Debt [Line Items]
Debt Instrument Maturity Period	[1]	May 2012
Debt instrument interest rate	[1]	5.38%	5.38%
May 2012 5.38% notes | Troms Offshore Supply AS
Debt [Line Items]
Debt instrument maturity, in years		12 years

[1] Troms Offshore debt requires semi-annual principal payments and has a 12 year maturity.