Debt Costs (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Debt [Line Items]
Interest and debt costs incurred, net of interest capitalized	$ 50,029	$ 43,814	$ 29,745
Interest costs capitalized	13,673	11,497	10,602
Total interest and debt costs	$ 63,702	$ 55,311	$ 40,347