Stock-Based Compensation (Details) (Stock Option Plan [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock Option Plan [Member]
Summary the stock option transactions
Number of Options Outstanding	233,787	260,660	303,632
Number of Options Granted	0	0	0
Number of Options Exercised	7,294	(8,910)	(9,796)
Number of Options Forfeited/canceled/expired	13,323	(17,963)	(33,176)
Number of Options Outstanding	213,170	233,787	260,660	303,632
Number of Options Vested and Exercisable	213,170
Weighted Average Exercise Price, Outstanding	$ 33.38	$ 34.69	$ 37.40
Weighted Average Exercise Price, Granted	$ 0	$ 0	$ 0
Weighted Average Exercise Price, Exercised	$ 34.80	$ 29.41	$ 27.26
Weighted Average Exercise Price, Forfeited/canceled/expired	$ 57.93	$ 54.35	$ 61.69
Weighted Average Exercise Price, Outstanding	$ 31.79	$ 33.38	$ 34.69	$ 37.40
Weighted Average Exercise Price Vested and Exercisable	$ 31.79
Weighted Average Remaining Contractual Term (Years)	1 year 2 months 12 days	2 years 1 month 6 days	3 years	3 years 7 months 6 days
Weighted Average Remaining Contractual Term (Years) Vested and Exercisable	1 year 2 months 12 days
Aggregate Intrinsic Value Outstanding	$ 4,058,035	$ 1,253,039	$ 135,886
Aggregate Intrinsic Value Outstanding	2,519,147	4,058,035	1,253,039	135,886
Aggregate Intrinsic Value Vested and Exercisable	$ 2,519,147