Stock-Based Compensation and Stock Options - Stock Options (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding, beginning balance, Shares	1,017,494	1,000,830	1,029,103	1,058,411
Options granted, Shares	41,650	50,450	86,825	97,475
Options exercised, Shares	(80,455)	(55,993)	(124,818)	(156,948)
Options cancelled/forfeited, Shares	(2,772)	(5,223)	(15,193)	(8,874)
Options outstanding, ending balance, Shares	975,917	990,064	975,917	990,064
Options outstanding, beginning balance, Weighted Average Exercise Price	$ 55.54	$ 47.05	$ 54.87	$ 45.17
Options granted, Weighted Average Exercise Price	79.49	87.49	65.55	79.17
Options exercised, Weighted Average Exercise Price	38.66	33.72	37.77	36.48
Options cancelled/forfeited, Weighted Average Exercise Price	54.70	51.52	57.09	51.24
Options outstanding, ending balance, Weighted Average Exercise Price	$ 57.97	$ 49.84	$ 57.97	$ 49.84