Share-Based Compensation (Details Textuals) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Years	Sep. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate			34.10%
Share-Based Compensation (Textuals) [Abstract]
Stock option granted			462,229
Estimated weighted- average grant date fair value of stock options			$ 5.48
Aggregate intrinsic value of stock options exercised	$ 360,000		$ 1,600,000
Actual tax benefit realized on options exercised	141,000		629,000
Nonvested common stock awards granted			68,900
Vesting rights of Performance-based shares			four
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Weighted Average Volatility Rate			34.10%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate			0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term			4.4
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate			0.62%
Director [Member]
Share-Based Compensation (Textuals) [Abstract]
Nonvested common stock awards granted			14,308
Employee Stock Option [Member]
Share-Based Compensation (Textuals) [Abstract]
Weighted-average period of recognition of unrecognized compensation cost			3.4
Total unrecognized compensation cost	5,800,000		5,800,000
Compensation cost charged against income	362,000	347,000	1,100,000	1,000,000
Income tax benefit recognized during the period	142,000	136,000	433,000	407,000
Nonvested Stock Awards [Member]
Share-Based Compensation (Textuals) [Abstract]
Weighted-average period of recognition of unrecognized compensation cost			2.7
Total unrecognized compensation cost	14,800,000		14,800,000
Compensation cost charged against income	2,100,000	3,700,000	9,100,000	5,600,000
Income tax benefit recognized during the period	805,000	1,500,000	3,600,000	2,200,000
Restricted Stock Units (RSUs) [Member]
Share-Based Compensation (Textuals) [Abstract]
Weighted-average period of recognition of unrecognized compensation cost			3.9
Total unrecognized compensation cost	5,600,000		5,600,000
Compensation cost charged against income	279,000
Income tax benefit recognized during the period	$ 109,000
Nonvested common stock awards granted			307,989