Equity-Based Compensation (Restricted Stock Awards Activity) (Details) (Restricted Stock [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding at beginning, shares	5,801	1,247
Outstanding at beginning, weighted-average grant date fair value	$ 43.21	$ 41.87
Granted, shares		5,264
Granted, weighted-average grant date fair value		$ 44.49	$ 34.58
Vested, shares	(1,509)	(489)
Vested, weighted-average grant date fair value	$ 42.96	$ 52.87
Forfeited, shares	(127)	(221)
Forfeited, weighted-average grant date fair value	$ 44.59	$ 44.95
Outstanding at end, shares	4,165	5,801	1,247
Outstanding at end, weighted-average grant date fair value	$ 43.25	$ 43.21	$ 41.87