Net Income Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Basic
Net income applicable to common stock	$ 8,019	$ 6,345	$ 15,590	$ 12,319
Average common shares outstanding (shares)	25,223,749	25,110,709	25,205,092	25,094,852
Net income per common share - basic (usd per share)	$ 0.32	$ 0.25	$ 0.62	$ 0.49
Diluted
Net income applicable to common stock	$ 8,019	$ 6,345	$ 15,590	$ 12,319
Average common shares outstanding (shares)	25,223,749	25,110,709	25,205,092	25,094,852
Effect of dilutive stock-based compensation (shares)	150,119	38,651	129,806	49,282
Average common shares outstanding - diluted	25,373,868	25,149,360	25,334,898	25,144,134
Net income per common share - diluted (usd per share)	$ 0.32	$ 0.25	$ 0.62	$ 0.49