Summary of Combined Fair Value of Assets Incurred Impairments (Detail) $ in Thousands		3 Months Ended		6 Months Ended
		Sep. 30, 2016 USD ($) Vessel Vehicle	Sep. 30, 2015 USD ($) Vessel	Sep. 30, 2016 USD ($) Vessel Vehicle	Sep. 30, 2015 USD ($) Vessel
Asset Impairment Charges [Abstract]
Number of vessels impaired during the period | Vessel		42	19	54	33
Number of ROVs impaired during the period | Vehicle		8		8
Amount of impairment incurred	[1]	$ 129,562	$ 31,672	$ 166,448	$ 46,630
Combined fair value of assets incurring impairment		$ 322,550	$ 107,445	$ 477,950	$ 154,300

[1] Refer to Note (15) for additional information regarding asset impairment charges.