Redeemable Noncontrolling Interests and Total Equity (Preferred Stock) (Details) (USD $)			3 Months Ended		0 Months Ended		12 Months Ended	0 Months Ended	3 Months Ended	12 Months Ended			0 Months Ended	1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Series A Preferred Stock	Dec. 31, 2011 Series A Preferred Stock	Jun. 30, 2011 Series B Preferred Stock	Oct. 13, 2008 Series B Preferred Stock	Dec. 31, 2012 Series B Preferred Stock	Oct. 13, 2008 Series C Preferred Stock	Dec. 31, 2012 Series C Preferred Stock	Dec. 31, 2012 Series C Preferred Stock	Dec. 31, 2009 Series C Preferred Stock	Dec. 31, 2011 Series C Preferred Stock	Oct. 13, 2008 Series B and C Preferred Stock	Jul. 31, 2006 Depositary Shares	Dec. 31, 2012 Depositary Shares
Class of Stock [Line Items]
Preferred stock dividend rate					10.00%		10.00%			10.00%
Shares Outstanding			44,000						519,882	519,882
Liquidation preference (per share)			$ 25,000				$ 1,000		$ 1,000	$ 1,000
Carrying Value	$ 1,508,000,000	$ 1,508,000,000	$ 1,100,000,000	$ 1,100,000,000	$ 8,100,000,000				$ 408,000,000	$ 408,000,000		$ 408,000,000
Preferred Stock, Other Disclosures
Stock issued during the period (in shares)						7,839,209		1,160,791						44,000,000
Stock purchase price													9,000,000,000	1,100,000,000
Preferred stock redemption price (per share)			$ 25,000						$ 1,100	$ 1,100					$ 25
Preferred stock dividend declared (per share)			$ 255.56						$ 25.00
Proceeds from issuance of preferred stock						8,100,000,000		900,000,000					9,000,000,000
Stock purchase price (per share)								$ 784
Stock redeemed (in shares)											640,909
Stock redeemed, value											$ 700,000,000