Net Income Per Common Share (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Net Income Per Common Share
Number of options outstanding (in shares)	199,306	172,880
Weighted average exercise price of options outstanding (in dollars per share)	$ 16.09	$ 15.63
Dilutive effect of stock options (in shares)	116,012	50,057