Investments In Marketable Securities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Debt securities:
Unsecured debentures	$ 975		$ 665
Certificates of deposit	645		576
Government debt securities	28		31
Subtotal	1,648		1,272
Equity securities:
Mutual funds	68		67
Common stock	1		1
Subtotal	69		68
Total available-for-sale	1,717		1,340
Equity securities:
Mutual funds	12		12
Total trading	12		12
TOTAL	1,729		1,352
Held-to-maturity Securities	11		4
Total marketable securities	1,740		1,356
Footnotes to Marketable Securities Detail Table [Abstract]
Amortized cost of commmon stock available-for-sale	1		4
Gain Loss On Marketable Securities
Losses included in earnings that relate to tradingsecurities held at the reporting date	0	1
Unrealized losses on available-for-sale securities included in other comprehensive income	0	(2)
Proceeds from sales of available-for-sale securities	1,523	1,237
Gross realized gains on sales	1	1
Level 1
Debt securities:
Unsecured debentures	0		0
Certificates of deposit	0		0
Government debt securities	0		0
Subtotal	0		0
Equity securities:
Mutual funds	1		0
Common stock	1		1
Subtotal	2		1
Total available-for-sale	2		1
Equity securities:
Mutual funds	12		12
Total trading	12		12
TOTAL	14		13
Level 2
Debt securities:
Unsecured debentures	975		665
Certificates of deposit	645		576
Government debt securities	28		31
Subtotal	1,648		1,272
Equity securities:
Mutual funds	67		67
Common stock	0		0
Subtotal	67		67
Total available-for-sale	1,715		1,339
Equity securities:
Mutual funds	0		0
Total trading	0		0
TOTAL	1,715		1,339
Level 3
Debt securities:
Unsecured debentures	0		0
Certificates of deposit	0		0
Government debt securities	0		0
Subtotal	0		0
Equity securities:
Mutual funds	0		0
Common stock	0		0
Subtotal	0		0
Total available-for-sale	0		0
Equity securities:
Mutual funds	0		0
Total trading	0		0
TOTAL	$ 0		$ 0