Employee Stock-Based Compensation and Benefit Plans (Schedule of Non-vested Stock Unit Activity) (Details) (Non-Vested Stock Unit Awards [Member], USD $)	12 Months Ended
	Dec. 31, 2011
Non-Vested Stock Unit Awards [Member]
Non-vested stock at December 31, 2010	1,172,312
Granted	1,666,793
Vested	(527,933)
Forfeited	(171,344)
Non-vested stock at December 31, 2011	2,139,828
Weighted-average grant date fair value, non-vested stock at December 31, 2010	$ 40.86
Weighted-average grant date fair value, granted	$ 72.33
Weighted-average grant date fair value, vested	$ 40.33
Weighted-average grant date fair value, forfeited	$ 54.69
Weighted-average grant date fair value, non-vested stock at December 31, 2011	$ 64.05