Summary Information about Stock Options Outstanding (Detail) (USD $)			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Range 1	Dec. 31, 2012 Range 2	Dec. 31, 2012 Range 3	Dec. 31, 2012 Range 4
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise, Prices, Lower Range			$ 5.92	$ 10.01	$ 15.01	$ 5.92
Range of Exercise, Prices, Upper Range			$ 10.00	$ 15.00	$ 19.92	$ 19.92
Options, Number Outstanding			112,968	1,110,451	289,328	1,512,747
Options, Weighted Average Remaining Contractual Life (in years)			9 months 29 days	4 years 9 months 22 days	6 years 10 months 21 days	4 years 10 months 28 days
Options, Weighted Average Exercise Price	$ 14.81	$ 13.78	$ 9.72	$ 14.05	$ 19.74	$ 14.81
Options, Number Exercisable			112,968	749,451	30,578	892,997
Options Exercisable, Weighted Average Exercise Price			$ 9.72	$ 14.02	$ 18.23	$ 13.62