Stock Based Compensation and Stock Options - Stock Options Outstanding and Exercisable (Detail) (USD $)	6 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options	1,136,073	1,118,530	1,115,984	1,191,251	1,199,630	1,100,952
Weighted Average Remaining Contractual Life	3 years 6 months 15 days
Outstanding Options - Weighted Average Exercise Price	$ 26.42	$ 25.60	$ 24.80	$ 20.39	$ 19.60	$ 18.65
Exercisable Options - Number of Exercisable Options	502,676
Exercisable Options - Weighted Average Exercise Price	$ 18.94
Range of Exercise Price, $7.78 to $21.61 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	$ 7.78
Range of Exercise Price, upper limit	$ 21.61
Number of Outstanding Options	285,172
Weighted Average Remaining Contractual Life	2 years 7 months 13 days
Outstanding Options - Weighted Average Exercise Price	$ 14.75
Exercisable Options - Number of Exercisable Options	262,773
Exercisable Options - Weighted Average Exercise Price	$ 14.20
Range of Exercise Price, $21.62 to $23.10 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	$ 21.62
Range of Exercise Price, upper limit	$ 23.10
Number of Outstanding Options	306,278
Weighted Average Remaining Contractual Life	3 years 11 months 9 days
Outstanding Options - Weighted Average Exercise Price	$ 22.79
Exercisable Options - Number of Exercisable Options	142,551
Exercisable Options - Weighted Average Exercise Price	$ 22.69
Range of Exercise Price, $23.11 to $34.77 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	$ 23.11
Range of Exercise Price, upper limit	$ 34.77
Number of Outstanding Options	265,323
Weighted Average Remaining Contractual Life	2 years 11 months 5 days
Outstanding Options - Weighted Average Exercise Price	$ 26.74
Exercisable Options - Number of Exercisable Options	96,052
Exercisable Options - Weighted Average Exercise Price	$ 26.05
Range of Exercise Price, $34.78 to $45.55 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	$ 34.78
Range of Exercise Price, upper limit	$ 45.55
Number of Outstanding Options	279,300
Weighted Average Remaining Contractual Life	4 years 7 months 13 days
Outstanding Options - Weighted Average Exercise Price	$ 42.02
Exercisable Options - Number of Exercisable Options	1,300
Exercisable Options - Weighted Average Exercise Price	$ 40.57