Quarterly report pursuant to Section 13 or 15(d)

Tracking Stock (Details)

v2.4.0.6
Tracking Stock (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2012
Dec. 31, 2011
Sep. 30, 2011
Dec. 31, 2010
Tracking Stock [Abstract]          
Stockholders' Equity Note, Stock Split, Conversion Ratio 0.05        
Cash and Cash Equivalents, at Carrying Value $ 1,793 $ 1,793 $ 847 $ 896 $ 1,353
Reattribution Of Cash Between Tracking Stocks   $ 0