Available-For-Sale Investments (Summary Of Contractual Maturities Of Available-For-Sale Securities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Available-For-Sale Investments [Abstract]
Less than one year	$ 821
Due in 1-5 years	335
Due after 10 years	40	[1]
Total	1,196
Asset-based securities that mature over time	$ 40

[1] Included in the maturity table is $40 million of asset-based securities that mature over time and are being reported at their final maturity dates