Stock Options and Stock-Based Compensation - Stock Options Outstanding and Exercisable (Detail) - $ / shares	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options	1,029,103	1,058,411	1,064,439	1,143,928
Weighted Average Remaining Contractual Life	3 years 3 months 10 days
Outstanding Options – Weighted Average Exercise Price	$ 54.87	$ 45.17	$ 39.45
Exercisable Options – Number of Exercisable Options	468,107
Exercisable Options – Weighted Average Exercise Price	$ 41.35
Range of Exercise Price, $20.08 to $43.32 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	20.08
Range of Exercise Price, upper limit	$ 43.32
Number of Outstanding Options	264,782
Weighted Average Remaining Contractual Life	2 years 2 months 8 days
Outstanding Options – Weighted Average Exercise Price	$ 31.41
Exercisable Options – Number of Exercisable Options	247,798
Exercisable Options – Weighted Average Exercise Price	$ 30.91
Range of Exercise Price, $43.33 to $57.75 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	43.33
Range of Exercise Price, upper limit	$ 57.75
Number of Outstanding Options	363,979
Weighted Average Remaining Contractual Life	2 years 10 months 28 days
Outstanding Options – Weighted Average Exercise Price	$ 52.58
Exercisable Options – Number of Exercisable Options	185,609
Exercisable Options – Weighted Average Exercise Price	$ 51.83
Range of Exercise Price, $57.76 to $77.93 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	57.76
Range of Exercise Price, upper limit	$ 77.93
Number of Outstanding Options	323,392
Weighted Average Remaining Contractual Life	4 years 14 days
Outstanding Options – Weighted Average Exercise Price	$ 68.83
Exercisable Options – Number of Exercisable Options	34,700
Exercisable Options – Weighted Average Exercise Price	$ 59.89
Range of Exercise Price, $77.94 to $88.22 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	77.94
Range of Exercise Price, upper limit	$ 88.22
Number of Outstanding Options	76,950
Weighted Average Remaining Contractual Life	5 years 6 months
Outstanding Options – Weighted Average Exercise Price	$ 87.76
Exercisable Options – Number of Exercisable Options	0
Exercisable Options – Weighted Average Exercise Price	$ 0