Investments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	$ 29,074	$ 25,366
Fixed maturities, Available for sale, Fair Value	30,734	26,456
Equity securities, Available for sale, Amortized Cost	1,283	931
Equity securities, Available for sale, Fair Value	1,501	1,123
U.S. Government and government agencies [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	347	310
Fixed maturities, Available for sale, Fair Value	353	314
Fixed maturities, Available for sale, Gross Unrealized, Gains	8	7
Fixed maturities, Available for sale, Gross Unrealized, Losses	(2)	(3)
States, municipalities and political subdivisions [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	6,393	5,360
Fixed maturities, Available for sale, Fair Value	6,747	5,372
Fixed maturities, Available for sale, Gross Unrealized, Gains	364	156
Fixed maturities, Available for sale, Gross Unrealized, Losses	(10)	(144)
Foreign government [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	184	198
Fixed maturities, Available for sale, Fair Value	194	208
Fixed maturities, Available for sale, Gross Unrealized, Gains	10	10
Fixed maturities, Available for sale, Gross Unrealized, Losses	0	0
Residential Mortgage Backed Securities [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	4,046	3,947
Fixed maturities, Available for sale, Fair Value	4,442	4,310
Fixed maturities, Available for sale, Gross Unrealized, Gains	411	391
Fixed maturities, Available for sale, Gross Unrealized, Losses	(15)	(28)
Commercial Mortgage Backed Securities [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	2,294	2,535
Fixed maturities, Available for sale, Fair Value	2,451	2,724
Fixed maturities, Available for sale, Gross Unrealized, Gains	158	192
Fixed maturities, Available for sale, Gross Unrealized, Losses	(1)	(3)
Asset-backed Securities [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	3,872	2,477
Fixed maturities, Available for sale, Fair Value	3,887	2,493
Fixed maturities, Available for sale, Gross Unrealized, Gains	37	35
Fixed maturities, Available for sale, Gross Unrealized, Losses	(22)	(19)
All other corporate [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	11,938	10,539
Fixed maturities, Available for sale, Fair Value	12,660	11,035
Fixed maturities, Available for sale, Gross Unrealized, Gains	751	604
Fixed maturities, Available for sale, Gross Unrealized, Losses	(29)	(108)
Fixed maturities [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	29,074	25,366
Fixed maturities, Available for sale, Fair Value	30,734	26,456
Fixed maturities, Available for sale, Gross Unrealized, Gains	1,739	1,395
Fixed maturities, Available for sale, Gross Unrealized, Losses	(79)	(305)
Common stocks [Member]
Available for sale fixed maturities and equity securities
Equity securities, Available for sale, Amortized Cost	885	665
Equity securities, Available for sale, Fair Value	1,087	858
Equity securities, Available for sale, Gross Unrealized, Gains	227	209
Equity securities, Available for sale, Gross Unrealized, Losses	(25)	(16)
Perpetual preferred stocks [Member]
Available for sale fixed maturities and equity securities
Equity securities, Available for sale, Amortized Cost	398	266
Equity securities, Available for sale, Fair Value	414	265
Equity securities, Available for sale, Gross Unrealized, Gains	21	9
Equity securities, Available for sale, Gross Unrealized, Losses	$ (5)	$ (10)

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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