Employee Stock Purchase Plan - Summary of Employee Stock Purchase Plan (Detail) - USD ($)	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Employee Stock Purchase Plan [Line Items]
Employee contributions	$ 534,000	$ 505,000	$ 503,000
Shares acquired	2,492,572
Employee Stock Purchase Plan [Member]
Employee Stock Purchase Plan [Line Items]
Shares acquired	6,007	8,451	8,271
Average purchase price	$ 88.85	$ 59.70	$ 59.55