Equity-based Incentive Plans (Details 2) (Stock options, USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stock options
Options
Balance at the beginning of the period (in shares)	7,406,393	6,489,371	7,986,681
Exercised (in shares)	(1,047,297)	(1,414,153)	(2,807,898)
Forfeited (in shares)	(499,718)	(214,757)	(326,519)
Balance at the end of the period (in shares)	8,602,282	7,406,393	6,489,371
Additional disclosures
Balance at the beginning of the period (in dollars per share)	$ 14.91	$ 13.69	$ 10.86
Granted (in dollars per share)	$ 14.34	$ 14.73	$ 15.04
Exercised (in dollars per share)	$ 11.37	$ 8.11	$ 5.81
Forfeited (in dollars per share)	$ 16.61	$ 20.35	$ 15.83
Balance at the end of the period (in dollars per share)	$ 15.06	$ 14.91	$ 13.69
Balance at the beginning of the period (in dollars per share)	$ 5.14	$ 5.09	$ 3.40
Granted (in dollars per share)	$ 5.36	$ 5.81	$ 5.14
Exercised (in dollars per share)	$ 4.28	$ 2.89	$ 2.57
Forfeited (in dollars per share)	$ 6.15	$ 6.33	$ 5.92
Balance at the end of the period (in dollars per share)	$ 5.25	$ 5.14	$ 5.09