Summary of Norwegian Kroner (NOK) Denominated Borrowings Outstanding (Detail) - Troms Offshore Supply AS NOK in Thousands, $ in Thousands		Mar. 31, 2017 USD ($)	Mar. 31, 2017 NOK	Mar. 31, 2016 USD ($)	Mar. 31, 2016 NOK
Debt [Line Items]
Amount outstanding		$ 92,000
3.81% January 2014 notes
Debt [Line Items]
Amount outstanding	[1]	26,167	NOK 225,000	$ 30,207	NOK 250,000
Fair value in U.S. dollar equivalent	[1]	26,133		30,199
5.38% May 2012 notes
Debt [Line Items]
Amount outstanding	[1]	14,864	NOK 127,800	17,500	NOK 144,840
Fair value in U.S. dollar equivalent	[1]	$ 14,793		$ 17,479

[1] Note requires semi-annual principal payments.