Summary Information about Stock Options Outstanding (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options, Weighted Average Exercise Price (In Dollars Per Share)	$ 21.52	$ 15.95
10.01 - 15.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise, Prices, Lower Range (In Dollars Per Share)	$ 10.01
Range of Exercise, Prices, Upper Range (In Dollars Per Share)	$ 15.00
Options, Number Outstanding (In Shares)	236,250
Options, Weighted Average Remaining Contractual Life (in years)	3 years 9 months 14 days
Options, Weighted Average Exercise Price (In Dollars Per Share)	$ 14.11
Options, Number Exercisable (In Shares)	236,250
Options Exercisable, Weighted Average Exercise Price (In Shares)	$ 14.11
15.01 - 20.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise, Prices, Lower Range (In Dollars Per Share)	$ 15.01
Range of Exercise, Prices, Upper Range (In Dollars Per Share)	$ 19.92
Options, Number Outstanding (In Shares)	112,500
Options, Weighted Average Remaining Contractual Life (in years)	5 years 1 month 24 days
Options, Weighted Average Exercise Price (In Dollars Per Share)	$ 19.92
Options, Number Exercisable (In Shares)	52,500
Options Exercisable, Weighted Average Exercise Price (In Shares)	$ 19.92
20.01 - 25.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise, Prices, Lower Range (In Dollars Per Share)	$ 20.01
Range of Exercise, Prices, Upper Range (In Dollars Per Share)	$ 25.00
Options, Number Outstanding (In Shares)	7,521
Options, Weighted Average Remaining Contractual Life (in years)	9 years 10 months 6 days
Options, Weighted Average Exercise Price (In Dollars Per Share)	$ 24.98
Options, Number Exercisable (In Shares)	0
Options Exercisable, Weighted Average Exercise Price (In Shares)	$ 0.00
25.01 - 30.29
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise, Prices, Lower Range (In Dollars Per Share)	$ 25,010.00
Range of Exercise, Prices, Upper Range (In Dollars Per Share)	$ 30,290.00
Options, Number Outstanding (In Shares)	267,243
Options, Weighted Average Remaining Contractual Life (in years)	9 years 7 months 13 days
Options, Weighted Average Exercise Price (In Dollars Per Share)	$ 28.65
Options, Number Exercisable (In Shares)	0
Options Exercisable, Weighted Average Exercise Price (In Shares)	$ 0.00
10.01 - 30.29
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise, Prices, Lower Range (In Dollars Per Share)	$ 10,010.00
Range of Exercise, Prices, Upper Range (In Dollars Per Share)	$ 30,290.00
Options, Number Outstanding (In Shares)	623,514
Options, Weighted Average Remaining Contractual Life (in years)	6 years 7 months 10 days
Options, Weighted Average Exercise Price (In Dollars Per Share)	$ 21.52
Options, Number Exercisable (In Shares)	288,750
Options Exercisable, Weighted Average Exercise Price (In Shares)	$ 15.16