Equity Compensation Plans - Additional Information (Detail) (USD $)	12 Months Ended					12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Stock Option Plan 2012	Apr. 30, 2012 Stock Option Plan 2012	Dec. 31, 2012 Stock Options	Dec. 31, 2012 Performance Based Restricted Stock Awards	Dec. 31, 2011 Performance Based Restricted Stock Awards	Dec. 31, 2010 Performance Based Restricted Stock Awards	Dec. 31, 2012 Restricted Stock	Dec. 31, 2011 Restricted Stock	Dec. 31, 2010 Restricted Stock	Dec. 31, 2012 Time Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share options and restricted shares authorized				1,750,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized				1,200,000
Stock based compensation expense	$ 1,400,000	$ 1,300,000	$ 1,400,000
Cash received from exercise of stock option	1,000,000	100,000	100,000
Tax Benefit From Stock Options						200,000
Total intrinsic value for options exercised	700,000	100,000
Number of options granted	147,000	177,500	200,775										73,750,000
Total unrecognized compensation cost				1,600,000						1,800,000
Weighted average expected amortization period				3 years 2 months 12 days						2 years 3 months 18 days
Restricted shares granted	188,000						114,500	22,000	116,000				73,750
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 7.79	$ 5.43	$ 4.48							$ 12.56	$ 5.54	$ 7.8
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period										171,369	59,440	83,000
Exercised	130,000	36,000	16,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value	600,000	600,000	400,000
Stock Repurchased During Period, Shares				309,667
Stock Repurchased During Period, Value	$ 3,998,000	$ 200,000	$ 111,000	$ 3,800,000
Share Price				$ 12.35
Stock Repurchase Program, Number of Shares Authorized to be Repurchased				690,333	1,000,000