Equity-Based Compensation (Performance Awards Activity) (Details) (Performance Awards [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Performance Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding at beginning, shares	1,120	430
Outstanding at beginning, weighted-average grant date fair value	$ 43.89	$ 24.14
Granted, shares	1,906	1,421
Granted, weighted-average grant date fair value	$ 42.28	$ 43.33	$ 19.46
Forfeited, shares	(173)	(716)
Forfeited, weighted-average grant date fair value	$ 42.90	$ 25.72
Paid out, shares	(224)	(15)
Paid out, weighted-average grant date fair value	$ 46.03	$ 64.57
Outstanding at end, shares	2,629	1,120	430
Outstanding at end, weighted-average grant date fair value	$ 42.52	$ 43.89	$ 24.14