Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Basic EPS:
Net income, as reported	$ 8,851	$ 9,561
Less allocated income to unvested shares	15	5
Net income available to common shareholders-basic	8,836	9,556
Basic weighted average common shares	18,281,353	18,140,749
Basic earnings per common share	$ 0.48	$ 0.53
Diluted EPS:
Net income available to common shareholders	$ 8,836	$ 9,556
Diluted weighted average common shares:
Basic weighted average common shares	18,281,353	18,140,749
Stock options and performance shares	408,489	395,230
Diluted weighted average common shares	18,689,842	18,535,979
Diluted earnings per common share	$ 0.47	$ 0.52