Summary of Information About Stock Options Granted Under Stock Incentive Plans (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, Lower Range	$ 5.92
Range of exercise prices, Upper Range	$ 44.60
Options, number outstanding	212,608
Options, weighted average remaining contractual life (in years)	1 year 8 months 1 day
Options, weighted average exercise price	$ 18.89
Options, number exercisable	208,932
Options exercisable, weighted average exercise price	$ 18.97
Range One
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, Lower Range	$ 5.92
Range of exercise prices, Upper Range	$ 10.65
Options, number outstanding	23,820
Options, weighted average remaining contractual life (in years)	6 months 15 days
Options, weighted average exercise price	$ 7.41
Options, number exercisable	23,820
Options exercisable, weighted average exercise price	$ 7.41
Range Two
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, Lower Range	$ 11.84
Range of exercise prices, Upper Range	$ 11.84
Options, number outstanding	18,750
Options, weighted average remaining contractual life (in years)	18 days
Options, weighted average exercise price	$ 11.84
Options, number exercisable	18,750
Options exercisable, weighted average exercise price	$ 11.84
Range Three
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, Lower Range	$ 12.19
Range of exercise prices, Upper Range	$ 12.19
Options, number outstanding	29,401
Options, weighted average remaining contractual life (in years)	11 months 5 days
Options, weighted average exercise price	$ 12.19
Options, number exercisable	29,401
Options exercisable, weighted average exercise price	$ 12.19
Range Four
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, Lower Range	$ 12.94
Range of exercise prices, Upper Range	$ 12.94
Options, number outstanding	21,663
Options, weighted average remaining contractual life (in years)	3 months
Options, weighted average exercise price	$ 12.94
Options, number exercisable	21,663
Options exercisable, weighted average exercise price	$ 12.94
Range Five
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, Lower Range	$ 14.28
Range of exercise prices, Upper Range	$ 14.31
Options, number outstanding	25,881
Options, weighted average remaining contractual life (in years)	4 years 1 month 24 days
Options, weighted average exercise price	$ 14.29
Options, number exercisable	22,205
Options exercisable, weighted average exercise price	$ 14.29
Range Six
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, Lower Range	$ 17.27
Range of exercise prices, Upper Range	$ 22.81
Options, number outstanding	19,251
Options, weighted average remaining contractual life (in years)	1 year 11 months 12 days
Options, weighted average exercise price	$ 21.55
Options, number exercisable	19,251
Options exercisable, weighted average exercise price	$ 21.55
Range Seven
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, Lower Range	$ 27.05
Range of exercise prices, Upper Range	$ 27.05
Options, number outstanding	55,508
Options, weighted average remaining contractual life (in years)	2 years 29 days
Options, weighted average exercise price	$ 27.05
Options, number exercisable	55,508
Options exercisable, weighted average exercise price	$ 27.05
Range Eight
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, Lower Range	$ 28.59
Range of exercise prices, Upper Range	$ 37.25
Options, number outstanding	8,334
Options, weighted average remaining contractual life (in years)	2 years 6 months 4 days
Options, weighted average exercise price	$ 33.79
Options, number exercisable	8,334
Options exercisable, weighted average exercise price	$ 33.79
Range Nine
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, Lower Range	$ 37.72
Range of exercise prices, Upper Range	$ 37.72
Options, number outstanding	5,000
Options, weighted average remaining contractual life (in years)	2 years 8 months 19 days
Options, weighted average exercise price	$ 37.72
Options, number exercisable	5,000
Options exercisable, weighted average exercise price	$ 37.72
Range Ten
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, Lower Range	$ 44.60
Range of exercise prices, Upper Range	$ 44.60
Options, number outstanding	5,000
Options, weighted average remaining contractual life (in years)	2 years 6 months 22 days
Options, weighted average exercise price	$ 44.60
Options, number exercisable	5,000
Options exercisable, weighted average exercise price	$ 44.60