Financial Instruments (Assets Measured At Fair Value On A Recurring Basis Using Unobservable Inputs (Level 3)) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Balance as of January 1	$ 2	$ 157
Transfers into Level 3		1
Transfers out of Level 3	(1)
Sales		(154)
Settlements		(2)
Balance as of December 31	1	2
Corporate And Asset Backed Debt Securities [Member]
Balance as of January 1	1	1
Transfers into Level 3
Transfers out of Level 3
Gains or (losses) included in earnings
Sales
Settlements
Balance as of December 31	1	1
Foreign Government Debt Securities [Member]
Balance as of January 1	1
Transfers into Level 3		1
Transfers out of Level 3	(1)
Balance as of December 31		1
Municipal Debt Securities (ARS) [Member]
Balance as of January 1		139
Gains or (losses) included in earnings		17
Sales		(154)
Settlements		(2)
ARS Rights [Member]
Balance as of January 1		17
Gains or (losses) included in earnings		$ (17)