Equity-based Incentive Plans (Details 2) (Stock options, USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock options
Options
Balance at the beginning of the period (in shares)	8,602,282	7,406,393	6,489,371
Granted (in shares)		2,742,904	2,545,932
Exercised (in shares)	(451,135)	(1,047,297)	(1,414,153)
Forfeited (in shares)	(1,077,438)	(499,718)	(214,757)
Balance at the end of the period (in shares)	7,073,709	8,602,282	7,406,393
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 15.06	$ 14.91	$ 13.69
Granted (in dollars per share)		$ 14.34	$ 14.73
Exercised (in dollars per share)	$ 6.70	$ 11.37	$ 8.11
Forfeited (in dollars per share)	$ 21.85	$ 16.61	$ 20.35
Balance at the end of the period (in dollars per share)	$ 14.56	$ 15.06	$ 14.91
Weighted Average Fair Value
Balance at the beginning of the period (in dollars per share)	$ 5.25	$ 5.14	$ 5.09
Granted (in dollars per share)		$ 5.36	$ 5.81
Exercised (in dollars per share)	$ 2.67	$ 4.28	$ 2.89
Forfeited (in dollars per share)	$ 6.04	$ 6.15	$ 6.33
Balance at the end of the period (in dollars per share)	$ 5.30	$ 5.25	$ 5.14