Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Assets pledged as collateral	$ 223	$ 0
Carrying value of debt measured at fair value	$ 2,548	$ 2,506
Preferred stock, par or stated value per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common Class A [Member]
Common stock, par or stated value per share	$ 0.01	$ 0.01
Common stock, shares authorized	4,000,000,000	4,000,000,000
Common stock, shares issued	515,543,332	549,361,673
Common stock, shares outstanding	515,543,332	549,361,673
Common Class B [Member]
Common stock, par or stated value per share	$ 0.01	$ 0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	28,969,735	28,989,160
Common stock, shares outstanding	28,969,735	28,989,160