Stock-Based Compensation and Stock Options - Stock Options (Detail) - $ / shares	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding, beginning balance, Shares	1,053,307	1,169,871	1,064,439	1,143,928
Options granted, Shares	145,150	154,500	261,750	305,550
Options exercised, Shares	(76,122)	(51,712)	(197,230)	(263,544)
Options cancelled/forfeited, Shares	(808)	(1,420)	(7,432)	(16,063)
Options outstanding, ending balance, Shares	1,121,527		1,121,527
Options outstanding, beginning balance, Weighted Average Exercise Price	$ 41.81	$ 38.41	$ 39.45	$ 32.02
Options granted, Weighted Average Exercise Price	59.32	57.75	56.72	52.49
Options exercised, Weighted Average Exercise Price	41.73	31.15	35.94	26.96
Options cancelled/forfeited, Weighted Average Exercise Price	40.37	$ 47.11	44.51	$ 40.90
Options outstanding, ending balance, Weighted Average Exercise Price	$ 44.08		$ 44.08