Schedule of Gain on Disposition of Assets (Detail) $ in Thousands	12 Months Ended
Mar. 31, 2017 USD ($) Vessel	Mar. 31, 2016 USD ($) Vessel	Mar. 31, 2015 USD ($) Vessel
Impaired Assets to be Disposed of by Method Other than Sale [Line Items]
Gain (loss) on vessels disposed	$ 24,099	$ 26,037	$ 23,796
Number of vessels disposed \| Vessel	12	17	13
Vessels
Impaired Assets to be Disposed of by Method Other than Sale [Line Items]
Gain (loss) on vessels disposed	$ (102)	$ 3,252	$ 2,988

Amount of gain (loss) on sale or disposal of property, plant and equipment assets, excluding oil and gas property and timber property.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1361-107760

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64862545&loc=d3e2941-110230

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