Available-For-Sale Investments (Reconciliation Of The Changes In Credit Losses Recognized In Earnings) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010		Dec. 31, 2009
Available-For-Sale Investments [Abstract]
Beginning balance of credit losses, January 1	$ 4	$ 2	[1]	$ 0	[1]
Additions for credit losses not previously recognized in earnings	1	2		2	[1]
Balance of credit losses, December 31	$ 5	$ 4		$ 2	[1]

[1] The standard was implemented April 1, 2009. Therefore, there are no credit losses recognized in the first quarter of 2009.