Stock Options and Stock-Based Compensation - Stock Options Outstanding and Exercisable (Detail) - $ / shares	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options	1,064,439	1,143,928	1,115,465	1,163,179
Weighted Average Remaining Contractual Life	3 years 4 months 24 days
Outstanding Options – Weighted Average Exercise Price	$ 39.45	$ 32.02	$ 30.36
Exercisable Options – Number of Exercisable Options	445,387
Exercisable Options – Weighted Average Exercise Price	$ 31.78
Range of Exercise Price, $12.71 to $32.10 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	12.71
Range of Exercise Price, upper limit	$ 32.10
Number of Outstanding Options	292,156
Weighted Average Remaining Contractual Life	2 years 10 months 2 days
Outstanding Options – Weighted Average Exercise Price	$ 24.96
Exercisable Options – Number of Exercisable Options	195,387
Exercisable Options – Weighted Average Exercise Price	$ 21.42
Range of Exercise Price, $32.11 to $34.78 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	32.11
Range of Exercise Price, upper limit	$ 34.78
Number of Outstanding Options	177,354
Weighted Average Remaining Contractual Life	2 years 10 months 28 days
Outstanding Options – Weighted Average Exercise Price	$ 34.41
Exercisable Options – Number of Exercisable Options	85,900
Exercisable Options – Weighted Average Exercise Price	$ 34.37
Range of Exercise Price, $34.79 to $44.86 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	34.79
Range of Exercise Price, upper limit	$ 44.86
Number of Outstanding Options	186,408
Weighted Average Remaining Contractual Life	3 years 2 months 8 days
Outstanding Options – Weighted Average Exercise Price	$ 41.20
Exercisable Options – Number of Exercisable Options	106,502
Exercisable Options – Weighted Average Exercise Price	$ 41.22
Range of Exercise Price, $44.87 to $57.75 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	44.87
Range of Exercise Price, upper limit	$ 57.75
Number of Outstanding Options	408,521
Weighted Average Remaining Contractual Life	4 years 4 months 17 days
Outstanding Options – Weighted Average Exercise Price	$ 52.58
Exercisable Options – Number of Exercisable Options	57,598
Exercisable Options – Weighted Average Exercise Price	$ 45.60