Disclosure of Accounted Total Revenues Percentage (Detail) - Sales Revenue, Net - Customer Concentration Risk		12 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Chevron Corporation
Entity Wide Revenue Major Customer [Line Items]
Total revenue percentage		16.30%	14.60%	12.70%
Freeport McMoRan
Entity Wide Revenue Major Customer [Line Items]
Total revenue percentage	[1]	11.30%	3.50%	1.60%
Petroleo Brasileiro Sa
Entity Wide Revenue Major Customer [Line Items]
Total revenue percentage		8.20%	11.00%	11.80%
Saudi Aramco
Entity Wide Revenue Major Customer [Line Items]
Total revenue percentage		10.00%	7.60%	5.40%
BP Plc
Entity Wide Revenue Major Customer [Line Items]
Total revenue percentage		5.80%	7.10%	10.10%

[1] A significant portion of this customer’s fiscal 2017 revenue was the result of the early termination of a long-term vessel charter contract.