Employee Stock Purchase Plan - Summary of Employee Stock Purchase Plan (Detail) (USD $)	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Employee Stock Purchase Plan [Line Items]
Employee contributions	$ 400,000	$ 346,000	$ 313,000
Shares acquired	2,439,296
Employee Stock Purchase Plan [Member]
Employee Stock Purchase Plan [Line Items]
Shares acquired	12,299	8,489	14,056
Average purchase price	$ 32.52	$ 40.71	$ 22.30