Stock Based-Compensation (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at January 1, 2012	726,224
Grants	154,970
Forfeitures	(2,704)
Vested and Issued	(178,297)
Balance at March 31, 2012	700,193
Weighted Average Grant Date Fair Value Per Share - Balance at January 1, 2012	$ 42.25
Weighted Average Grant Date Fair Value Per Share - Grants	$ 53.22
Weighted Average Grant Date Fair Value Per Share - Foreitures	$ 40.95
Weighted Average Grant Date Fair Value Per Share - Vested and issued	$ 28.51
Weighted Average Grant Date Fair Value Per Share - Balance at March 31, 2012	$ 48.04