Summary of Norwegian Kroner (NOK) Denominated Borrowings Outstanding (Detail) NOK in Thousands, $ in Thousands		Dec. 31, 2015 USD ($)	Dec. 31, 2015 NOK	Mar. 31, 2015 USD ($)	Mar. 31, 2015 NOK
3.81% January 2014 notes
Debt [Line Items]
Long-term debt outstanding	[1]	$ 29,606	NOK 262,500	$ 34,234	NOK 275,000
Fair value in U.S. dollar equivalent (Level 2)	[1]	29,612		34,226
5.38% May 2012 notes
Debt [Line Items]
Long-term debt outstanding	[1]	16,336	NOK 144,840	20,152	161,880
Fair value in U.S. dollar equivalent (Level 2)	[1]	$ 16,329		19,924
Variable rate borrowings, June 2013 borrowing agreement
Debt [Line Items]
Long-term debt outstanding	[2],[3]			3,112	25,000
Variable rate borrowings, May 2012 borrowing agreement
Debt [Line Items]
Long-term debt outstanding	[2],[4]			$ 2,490	NOK 20,000

[1] Notes require semi-annual principal payments.

[2] Fair values approximate carrying values because the borrowings bear interest at variable rates.

[3] Remaining note balance was repaid in September 2015. The company recognized a $0.1 million gain on early extinguishment

[4] Note was repaid in May 2015 upon maturity.