Accumulated Other Comprehensive Loss (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Net unrealized appreciation, securities pre-tax:
Net unrealized appreciation (depreciation) on securities arising during the period pre-tax	$ 162	$ 198	$ 177	$ 325
Reclassification adjustment for (gains) losses included in shareholders' net income pre-tax	(30)	(18)	(54)	(37)
Net unrealized appreciation (depreciation), securities pre-tax	132	180	123	288
Net unrealized appreciation (depreciation) derivatives pre-tax	(7)	24	(15)	30
Net translation of foreign currencies pre-tax	54	(59)	114	(53)
Postretirement benefits liability adjustment pre-tax:
Reclassification adjustment for amortization of net losses from past experience and prior service costs pre-tax	6	2	11	5
Net change due to valuation update pre-tax	3	(157)	3	(157)
Net postretirement benefits liability adjustment pre-tax	9	(155)	14	(152)
Net unrealized appreciation, securities tax:
Net unrealized appreciation (depreciation) on securities arising during the period tax	(55)	(69)	(60)	(111)
Reclasification adjustment for (gains) losses included in shareholders' net income tax	10	7	18	13
Net unrealized appreciation (depreciation), securities tax	(45)	(62)	(42)	(98)
Net unrealized appreciation (depreciation) derivatives tax	2	(8)	5	(10)
Net translation of foreign currencies tax	(8)	16	(16)	14
Postretirement benefits liability adjustment tax:
Reclassification adjustment for amortization of net losses from past experience and prior service costs tax	(3)	0	(4)	5
Net change due to valuation update tax	(1)	55	(1)	55
Net postretirement benefits liability adjustment tax	(4)	55	(5)	60
Net realized appreciation, securities after-tax:
Net unrealized appreciation (depreciation) on securities arising during the period after-tax	107	129	117	214
Reclassification adjustment for (gains) losses included in shareholders' net income after-tax	(20)	(11)	(36)	(24)
Net unrealized appreciation (depreciation), securities after-tax	87	118	81	190
Net unrealized appreciation (depreciation), derivatives after-tax	(5)	16	(10)	20
Net translation of foreign currencies after-tax	46	(43)	98	(39)
Postretirement benefits liability adjustment after-tax:
Reclassification adjustment for amortization of net losses from past experience and prior service costs after-tax	3	2	7	10
Net change due to valuation update after-tax	2	(102)	2	(102)
Net postretirement benefits liability adjustment after-tax	$ 5	$ (100)	$ 9	$ (92)