Investments In Marketable Securities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Debt securities:
Unsecured debentures	$ 440		$ 440		$ 665
Certificates of deposit	338		338		576
Government debt securities	26		26		31
Subtotal	804		804		1,272
Equity securities:
Mutual funds	52		52		67
Common stock	1		1		1
Subtotal	53		53		68
Total available-for-sale	857		857		1,340
Equity securities:
Mutual funds	12		12		12
Total trading	12		12		12
TOTAL	869		869		1,352
Held-to-maturity Securities	4		4		4
Total marketable securities	873		873		1,356
Footnotes to Marketable Securities Detail Table [Abstract]
Amortized cost of commmon stock available-for-sale	1		1		4
Gain Loss On Marketable Securities
Gains included in earnings that relate to trading securities held at the reporting date	0	(2)	0	(1)
Unrealized gains (losses) on available-for-sale securities included in other comprehensive income	(1)	(1)	(1)	(4)
Proceeds from sales of available-for-sale securities	1,513	1,134	5,160	4,218
Gross realized gains on sales	0	1	1	5
Level 1
Debt securities:
Unsecured debentures	0		0		0
Certificates of deposit	0		0		0
Government debt securities	0		0		0
Subtotal	0		0		0
Equity securities:
Mutual funds	0		0		0
Common stock	1		1		1
Subtotal	1		1		1
Total available-for-sale	1		1		1
Equity securities:
Mutual funds	12		12		12
Total trading	12		12		12
TOTAL	13		13		13
Level 2
Debt securities:
Unsecured debentures	440		440		665
Certificates of deposit	338		338		576
Government debt securities	26		26		31
Subtotal	804		804		1,272
Equity securities:
Mutual funds	52		52		67
Common stock	0		0		0
Subtotal	52		52		67
Total available-for-sale	856		856		1,339
Equity securities:
Mutual funds	0		0		0
Total trading	0		0		0
TOTAL	856		856		1,339
Level 3
Debt securities:
Unsecured debentures	0		0		0
Certificates of deposit	0		0		0
Government debt securities	0		0		0
Subtotal	0		0		0
Equity securities:
Mutual funds	0		0		0
Common stock	0		0		0
Subtotal	0		0		0
Total available-for-sale	0		0		0
Equity securities:
Mutual funds	0		0		0
Total trading	0		0		0
TOTAL	$ 0		$ 0		$ 0