Stockholders' Equity - Changes in Equity (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 1,911,000,000	$ 1,950,000,000	$ 1,948,000,000	$ 1,838,000,000
Total comprehensive income	111,000,000	89,000,000	190,000,000	231,000,000
Preferred stock dividends	(6,000,000)	(8,000,000)	(21,000,000)	(23,000,000)
Common stock dividends	(7,000,000)	(7,000,000)	(22,000,000)	(22,000,000)
Distributions to noncontrolling interests	(6,000,000)	(1,000,000)	(11,000,000)	(9,000,000)
Common stock share repurchases	(2,000,000)		(88,000,000)
Repurchase of equity awards	(2,000,000)		(2,000,000)
Adjustments to paid-in capital for purchase of noncontrolling interests			6,000,000
Adjustments to other comprehensive income for purchase of noncontrolling interests			(3,000,000)
Purchase of noncontrolling interests			(9,000,000)
Stock compensation	10,000,000	4,000,000	25,000,000	13,000,000
Stock withheld for employee taxes			(4,000,000)	(1,000,000)
Ending Balance	1,335,000,000	2,027,000,000	1,335,000,000	2,027,000,000
Attributable to Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	1,813,000,000	1,851,000,000	1,843,000,000	1,737,000,000
Total comprehensive income	106,000,000	83,000,000	178,000,000	219,000,000
Preferred stock dividends	(6,000,000)	(8,000,000)	(21,000,000)	(23,000,000)
Common stock dividends	(7,000,000)	(7,000,000)	(22,000,000)	(22,000,000)
Common stock share repurchases	(2,000,000)		(88,000,000)
Repurchase of equity awards	(2,000,000)		(2,000,000)
Adjustments to paid-in capital for purchase of noncontrolling interests			6,000,000
Adjustments to other comprehensive income for purchase of noncontrolling interests			(3,000,000)
Stock compensation	10,000,000	4,000,000	25,000,000	13,000,000
Stock withheld for employee taxes			(4,000,000)	(1,000,000)
Ending Balance	1,238,000,000	1,923,000,000	1,238,000,000	1,923,000,000
Attributable to Non-Controlling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	98,000,000	99,000,000	105,000,000	101,000,000
Total comprehensive income	5,000,000	6,000,000	12,000,000	12,000,000
Distributions to noncontrolling interests	(6,000,000)	(1,000,000)	(11,000,000)	(9,000,000)
Purchase of noncontrolling interests			(9,000,000)
Ending Balance	97,000,000	104,000,000	97,000,000	104,000,000
Accelerated Share Repurchase Program [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock share repurchases	(200,000,000)		(200,000,000)
Adjustments to paid-in capital for purchase of noncontrolling interests	40,000,000
Accelerated Share Repurchase Program [Member] | Attributable to Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock share repurchases	(200,000,000)		(200,000,000)
Series B Preferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Prefeerred stock share repurchases	(474,000,000)		(474,000,000)
Series B Preferred Stock | Attributable to Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Prefeerred stock share repurchases	$ (474,000,000)		$ (474,000,000)