Stock-Based Compensation and Stock Options - Stock Options (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding, beginning balance, Shares	1,000,830	1,063,254	1,058,411	1,064,439
Options granted, Shares	50,450	59,800	97,475	116,600
Options exercised, Shares	(55,993)	(66,870)	(156,948)	(121,108)
Options cancelled/forfeited, Shares	(5,223)	(2,877)	(8,874)	(6,624)
Options outstanding, ending balance, Shares	990,064	1,053,307	990,064	1,053,307
Options outstanding, beginning balance, Weighted Average Exercise Price	$ 47.05	$ 40.43	$ 45.17	$ 39.45
Options granted, Weighted Average Exercise Price	87.49	57.35	79.17	53.48
Options exercised, Weighted Average Exercise Price	33.72	33.50	36.48	32.30
Options cancelled/forfeited, Weighted Average Exercise Price	51.52	40.45	51.24	45.32
Options outstanding, ending balance, Weighted Average Exercise Price	$ 49.84	$ 41.81	$ 49.84	$ 41.81