Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Options
Outstanding at beginning of period	2,244
Granted	180
Exercised	(755)
Cancelled and expired	(23)
Outstanding at end of period	1,646	2,244
Exercisable at end of period	1,156
Options vested and expected to vest at end of period	1,594
Weighted-Average Exercise Price
Outstanding at beginning of period	$ 20.55
Granted	106.10
Exercised	14.12
Cancelled and expired	73.50
Outstanding at end of period	32.09	$ 20.55
Exercisable at end of period	18.26
Options vested and expected to vest at end of period	$ 31.06
Weighted-Average Remaining Contractual Term (years)
Outstanding	5 years 5 months 16 days	5 years 2 months 9 days
Exercisable at end of period	4 years 4 months 10 days
Options vested and expected to vest at end of period	5 years 4 months 13 days
Aggregate Intrinsic Value
Outstanding at end of period	$ 153,254
Exercisable at end of period	123,592
Options vested and expected to vest at end of period	$ 150,056