Stock Based-Compensation (Details 2) (USD $)	6 Months Ended
	Jun. 30, 2012	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at January 1, 2012		726,224
Grants	156,470
Forfeitures	(4,904)
Vested and Issued	(241,508)
Balance at June 30, 2012	636,282	726,224
Weighted Average Grant Date Fair Value Per Share - Balance at January 1, 2012		$ 42.25
Weighted Average Grant Date Fair Value Per Share - Grants	$ 53.26
Weighted Average Grant Date Fair Value Per Share - Forfeitures	$ 43.78
Weighted Average Grant Date Fair Value Per Share - Vested and issued	$ 33.64
Weighted Average Grant Date Fair Value Per Share - Balance at March 31, 2012	$ 48.05	$ 42.25