Stock Based Compensation and Stock Options - Stock Options Outstanding and Exercisable (Detail) - $ / shares	9 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Mar. 31, 2016
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options	1,169,871	1,068,503	1,143,928	1,238,863	1,102,919	1,115,465
Weighted Average Remaining Contractual Life	3 years 5 months 4 days
Outstanding Options - Weighted Average Exercise Price	$ 38.41	$ 35.28	$ 32.02	$ 32.17	$ 32.17	$ 29.67
Exercisable Options - Number of Exercisable Options	430,321
Exercisable Options - Weighted Average Exercise Price	$ 30.90
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	332,432
Weighted Average Remaining Contractual Life	2 years 10 months 2 days
Outstanding Options - Weighted Average Exercise Price	$ 25.04
Exercisable Options - Number of Exercisable Options	197,354
Exercisable Options - Weighted Average Exercise Price	$ 20.21
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	251,836
Weighted Average Remaining Contractual Life	2 years 10 months 28 days
Outstanding Options - Weighted Average Exercise Price	$ 34.51
Exercisable Options - Number of Exercisable Options	79,609
Exercisable Options - Weighted Average Exercise Price	$ 34.34
Range of Exercise Price, $34.79 to $45.55 [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	$ 45.55
Number of Outstanding Options	242,755
Weighted Average Remaining Contractual Life	2 years 11 months 15 days
Outstanding Options - Weighted Average Exercise Price	$ 41.96
Exercisable Options - Number of Exercisable Options	140,076
Exercisable Options - Weighted Average Exercise Price	$ 42.60
Range of Exercise Price, $45.56 to $57.75 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	45.56
Range of Exercise Price, upper limit	$ 57.75
Number of Outstanding Options	342,848
Weighted Average Remaining Contractual Life	4 years 8 months 26 days
Outstanding Options - Weighted Average Exercise Price	$ 52.29
Exercisable Options - Number of Exercisable Options	13,282
Exercisable Options - Weighted Average Exercise Price	$ 22.87