Available-For-Sale Investments (Summary Of Contractual Maturities Of Available-For-Sale Securities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Available-For-Sale Investments [Abstract]
Less than one year	$ 835
Due in 1-5 years	320
Due in 5-10 years	0
Due after 10 years	44	[1]
Total	1,199
Asset-based securities that mature over time	$ 35

[1] Included in the maturity table is $35 million of asset-based securities that mature over time and are being reported at their final maturity dates.