Summary of Stock Option Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
	Sep. 30, 2022 USD ($) $ / shares shares	Mar. 31, 2021 $ / shares shares
Options
Outstanding at beginning of period | shares
Granted | shares	5
Exercised | shares	(21)
Cancelled and expired | shares	(3)
Outstanding at end of period | shares	576	595
Exercisable at end of period | shares	500
Options vested and expected to vest at end of period | shares	576
Outstanding at beginning of period | $ / shares
Granted | $ / shares	$ 267.96
Exercised | $ / shares	93.07
Cancelled and expired | $ / shares	285.00
Outstanding at end of period | $ / shares	182.01	$ 178.54
Exercisable at end of period | $ / shares	169.15
Options vested and expected to vest at end of period | $ / shares	$ 182.01
Outstanding	5 years 1 month 20 days	5 years 6 months 18 days
Exercisable at end of period	4 years 7 months 20 days
Options vested and expected to vest at end of period	5 years 1 month 20 days
Outstanding at end of period | $	$ 49,789
Exercisable at end of period | $	49,167
Options vested and expected to vest at end of period | $	$ 49,789