Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
	Sep. 30, 2016	Mar. 31, 2016
Options
Outstanding at beginning of period	2,244
Granted	138
Exercised	(434)
Cancelled and expired	(12)
Outstanding at end of period	1,936	2,244
Exercisable at end of period	1,448
Options vested and expected to vest at end of period	1,893
Weighted-Average Exercise Price
Outstanding at beginning of period	$ 20.55
Granted	103.32
Exercised	13.29
Cancelled and expired	53.34
Outstanding at end of period	27.87	$ 20.55
Exercisable at end of period	17.16
Options vested and expected to vest at end of period	$ 27.12
Weighted-Average Remaining Contractual Term (years)
Outstanding	5 years 6 months 7 days	5 years 2 months 9 days
Exercisable at end of period	4 years 6 months 22 days
Options vested and expected to vest at end of period	5 years 5 months 12 days
Aggregate Intrinsic Value
Outstanding at end of period	$ 195,015
Exercisable at end of period	161,380
Options vested and expected to vest at end of period	$ 192,059