Schedule I - Condensed Parent Company Financial Statements (Condensed Statements Of Cash Flows) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net income	$ 1,714	$ 1,323	$ 1,085
Net cash provided by operating activities	3,672	4,511	3,463
Purchases of available-for-sale securities	(3,194)	(2,166)	(3,013)
Proceeds from sales and maturities of available-for-sale securities	3,063	2,261	2,988
Other	21	(4)	(12)
Net cash used in investing activities	(4,434)	(4,423)	(4,492)
Proceeds from the issuance of long-term debt	2,570	2,738	4,409
Proceeds from the issuance of common stock related to employee benefit plans	67	302	519
Payments for the redemption of long-term debt	(278)	(1,647)	(1,533)
Notes payable and commercial paper	208	(55)	(548)
Dividends paid	(1,329)	(1,284)	(1,222)
Other	(10)	(4)	(3)
Net cash provided by (used in) financing activities	1,202	40	1,585
Net increase (decrease) in cash and cash equivalents	440	128	556
Cash and cash equivalents at beginning of period	1,670	1,542	986
Cash and cash equivalents at end of period	2,110	1,670	1,542
Parent Company [Member]
Net income	1,706	1,320	1,075
Adjustments to reconcile net income to net cash provided by operating activities	(1,993)	(1,142)	(1,002)
Net cash provided by operating activities	(287)	178	73
Purchases of available-for-sale securities	(45)
Proceeds from sales and maturities of available-for-sale securities	105	36	17
Distributions from wholly-owned subsidiaries	299	350
Investment in wholly-owned subsidiary			(250)
Notes receivable from affiliates, net	264	263	(272)
Other	14	6	9
Net cash used in investing activities	637	655	(496)
Proceeds from the issuance of long-term debt	996	522	1,740
Proceeds from the issuance of common stock related to employee benefit plans	67	302	519
Payments for the redemption of long-term debt		(274)
Notes payable and commercial paper	151	(2)	(269)
Notes payable to affiliate	105
Dividends paid	(1,329)	(1,284)	(1,222)
Other	17	26	15
Net cash provided by (used in) financing activities	7	(710)	783
Net increase (decrease) in cash and cash equivalents	357	123	360
Cash and cash equivalents at beginning of period	488	365	5
Cash and cash equivalents at end of period	$ 845	$ 488	$ 365