Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings per share, basic and diluted
Net income	$ 7,121	$ 4,884	$ 20,127	$ 16,108
Basic weighted average common shares	18,173,062	18,294,040	18,154,690	18,306,516
Basic earnings per common share	$ 0.39	$ 0.27	$ 1.11	$ 0.88
Stock options	409,382	405,207	408,108	451,613
Restricted stock	1,363	9,474	9,281	8,604
Long term incentive plan	173		4,326
Diluted weighted average common shares	18,583,980	18,708,721	18,576,405	18,766,733
Diluted earnings per common share	$ 0.38	$ 0.26	$ 1.08	$ 0.86
Basic EPS [Member]
Earnings per share, basic and diluted
Net income	7,121	4,884	20,127	16,108
Basic weighted average common shares	18,173,062	18,294,040	18,154,690	18,306,516
Basic earnings per common share	$ 0.39	$ 0.27	$ 1.11	$ 0.88
Diluted EPS [Member]
Earnings per share, basic and diluted
Net income	$ 7,121	$ 4,884	$ 20,127	$ 16,108