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Summary of Debt Outstanding (Parenthetical) (Detail)		6 Months Ended
		Sep. 30, 2016	Mar. 31, 2016
May 2015 4.22% Notes
Debt [Line Items]
Debt instrument interest rate	[1]	4.22%	4.22%
May 2015 4.22% Notes | Troms Offshore Supply AS
Debt [Line Items]
Debt instrument maturity, in years		12 years
March 2015 4.21% Notes
Debt [Line Items]
Debt instrument interest rate	[1]	4.21%	4.21%
March 2015 4.21% 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.

X

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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+ References

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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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