Earnings Per Share (Details) (USD $)	3 Months Ended												12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share Details
Weighted average shares outstanding													1,663,147	1,652,861	1,642,469
Effect of dilutive stock options outstanding													58	858	912
Diluted weighted average shares outstanding													1,663,205	1,653,719	1,643,381
Basic earnings per share	$ 1.01	$ 0.74	$ 1.15	$ 0.70	$ 0.85	$ 0.85	$ 0.74	$ 0.78	$ 0.81	$ 0.81	$ 0.73	$ 0.53	$ 3.61	$ 3.21	$ 2.89
Diluted earnings per share	$ 1.01	$ 0.74	$ 1.15	$ 0.70	$ 0.85	$ 0.84	$ 0.74	$ 0.78	$ 0.81	$ 0.81	$ 0.73	$ 0.53	$ 3.61	$ 3.21	$ 2.89