Stock-Based Compensation (Details) (Stock Option Plan [Member], USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Stock Option Plan [Member]
Summary the stock option transactions
Number of Options Outstanding at begining	260,660
Number of Options Exercised	(3,486)
Number of Options Outstanding at ending	257,174	260,660
Number of Options Exercisable	257,174
Weighted Average Exercise Price, Outstanding at January 1, 2013	$ 34.69
Weighted Average Exercise Price, Exercised	$ 28.47
Weighted Average Exercise Price Outstanding at March 31, 2013	$ 34.77	$ 34.69
Weighted Average Exercise Price Exercisable at March 31, 2013	$ 34.77
Weighted Average Remaining Contractual Term (Years)	2 years 8 months 12 days	3 years
Weighted Average Remaining Contractual Term (Years) Exercisable	2 years 8 months 12 days
Aggregate Intrinsic Value Outstanding at January 1, 2013	$ 1,253,039
Aggregate Intrinsic Value Outstanding at March 31, 2013	3,287,930	1,253,039
Aggregate Intrinsic Value exercisable	$ 3,287,930