Debt Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Debt Disclosure [Abstract]
Interest and debt costs incurred, net of interest capitalized	$ 75,026	$ 53,752	$ 50,029
Interest costs capitalized	4,829	10,451	13,673
Total interest and debt costs	$ 79,855	$ 64,203	$ 63,702