Stock Based Compensation and Stock Options - Stock Options Outstanding and Exercisable (Detail) - $ / shares	3 Months Ended
	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Mar. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options	1,167,042	1,163,179	1,118,530	1,115,984
Weighted Average Remaining Contractual Life	3 years 3 months 22 days
Outstanding Options - Weighted Average Exercise Price	$ 28.15	$ 27.65	$ 25.60	$ 24.80
Exercisable Options - Number of Exercisable Options	563,591
Exercisable Options - Weighted Average Exercise Price	$ 22.12
Range of Exercise Price, $7.78 to $22.07 [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	$ 22.07
Number of Outstanding Options	292,151
Weighted Average Remaining Contractual Life	3 years 3 months 18 days
Outstanding Options - Weighted Average Exercise Price	$ 16.49
Exercisable Options - Number of Exercisable Options	252,127
Exercisable Options - Weighted Average Exercise Price	$ 15.65
Range of Exercise Price, $22.08 to $24.24 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	22.08
Range of Exercise Price, upper limit	$ 24.24
Number of Outstanding Options	325,780
Weighted Average Remaining Contractual Life	2 years 5 months 27 days
Outstanding Options - Weighted Average Exercise Price	$ 23.45
Exercisable Options - Number of Exercisable Options	197,068
Exercisable Options - Weighted Average Exercise Price	$ 23.47
Range of Exercise Price, $24.25 to $35.77 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	24.25
Range of Exercise Price, upper limit	$ 35.77
Number of Outstanding Options	304,149
Weighted Average Remaining Contractual Life	3 years 8 months 5 days
Outstanding Options - Weighted Average Exercise Price	$ 33.02
Exercisable Options - Number of Exercisable Options	71,783
Exercisable Options - Weighted Average Exercise Price	$ 28.24
Range of Exercise Price, $35.78 to $45.55 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	35.78
Range of Exercise Price, upper limit	$ 45.55
Number of Outstanding Options	244,962
Weighted Average Remaining Contractual Life	3 years 11 months 9 days
Outstanding Options - Weighted Average Exercise Price	$ 42.25
Exercisable Options - Number of Exercisable Options	42,613
Exercisable Options - Weighted Average Exercise Price	$ 43.74