Earnings Per Common Share (Calculation of Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Net income	$ 35,074	$ 29,724	$ 24,051
Dividends and undistributed earnings allocated to participating securities	(160)	(112)	(65)
Net income applicable to common shareholders	$ 34,914	$ 29,612	$ 23,986
Weighted average common shares outstanding - basic (in shares)	16,358	16,254	16,114
Dilutive effect of common stock equivalents (in shares)	43	30	9
Weighted average common shares outstanding - diluted (in shares)	16,401	16,284	16,123
Basic earnings per common share (in dollars per share)	$ 2.13	$ 1.82	$ 1.49
Diluted earnings per common share (in dollars per share)	$ 2.13	$ 1.82	$ 1.49
Antidilutive common stock equivalents	357	371	758