Stock-Based Compensation and Stock Options - Outstanding Options (Detail) - USD ($)	3 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding, beginning balance, Shares	1,029,103	1,058,411
Granted, Number of Options	45,175	47,025
Exercised, Number of Options	(44,363)	(100,955)
Cancelled - forfeited, Number of Options	(10,951)
Cancelled - expired, Number of Options	(1,470)
Options outstanding, ending balance, Shares	1,017,494	1,000,830
Ending vested and expected to vest, Number of Options	865,307
Ending exercisable, Number of Options	459,763
Options outstanding, beginning balance, Weighted Average Exercise Price	$ 54.87	$ 45.17
Granted, Weighted Average Exercise Price per Share	52.69	70.24
Exercised, Weighted Average Exercise Price per Share	36.15	38.01
Cancelled - forfeited, Weighted Average Exercise Price per Share	61.34
Cancelled - expired, Weighted Average Exercise Price per Share	41.44
Options outstanding, ending balance, Weighted Average Exercise Price	55.54	$ 47.05
Ending vested and expected to vest, Weighted Average Exercise Price per Share	48.31
Ending exercisable, Weighted Average Exercise Price per Share	$ 43.07
Option outstanding, Weighted Average Remaining Contractual Life (Years)	3 years 2 months 23 days
Ending vested and expected to vest, Weighted Average Remaining Contractual Life (Years)	2 years 10 months 24 days
Ending exercisable, Weighted Average Remaining Contractual Life (Years)	2 years 4 months 20 days
Option outstanding, Aggregate Intrinsic Value	$ 17,853,276
Ending vested and expected to vest, Aggregate Intrinsic Value	14,950,515
Ending exercisable, Aggregate Intrinsic Value	$ 12,792,666