Investments (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	$ 31,868	$ 29,074
Available for sale (AFS) fixed maturities	33,114	30,734
Equity securities, Available for sale, Amortized Cost	1,590	1,283
Equity securities, Available for sale, Fair Value	1,658	1,501
U.S. Government and government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	329	347
Available for sale (AFS) fixed maturities	335	353
Fixed maturities, Available for sale, Gross Unrealized, Gains	8	8
Fixed maturities, Available for sale, Gross Unrealized, Losses	(2)	(2)
States, municipalities and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	6,874	6,393
Available for sale (AFS) fixed maturities	7,166	6,747
Fixed maturities, Available for sale, Gross Unrealized, Gains	321	364
Fixed maturities, Available for sale, Gross Unrealized, Losses	(29)	(10)
Foreign government [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	157	184
Available for sale (AFS) fixed maturities	166	194
Fixed maturities, Available for sale, Gross Unrealized, Gains	9	10
Fixed maturities, Available for sale, Gross Unrealized, Losses	0	0
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	3,540	4,046
Available for sale (AFS) fixed maturities	3,879	4,442
Fixed maturities, Available for sale, Gross Unrealized, Gains	354	411
Fixed maturities, Available for sale, Gross Unrealized, Losses	(15)	(15)
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	2,185	2,294
Available for sale (AFS) fixed maturities	2,297	2,451
Fixed maturities, Available for sale, Gross Unrealized, Gains	112	158
Fixed maturities, Available for sale, Gross Unrealized, Losses	0	(1)
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	4,673	3,872
Available for sale (AFS) fixed maturities	4,701	3,887
Fixed maturities, Available for sale, Gross Unrealized, Gains	47	37
Fixed maturities, Available for sale, Gross Unrealized, Losses	(19)	(22)
All other corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	14,110	11,938
Available for sale (AFS) fixed maturities	14,570	12,660
Fixed maturities, Available for sale, Gross Unrealized, Gains	606	751
Fixed maturities, Available for sale, Gross Unrealized, Losses	(146)	(29)
Fixed maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Available for sale, Amortized Cost	31,868	29,074
Available for sale (AFS) fixed maturities	33,114	30,734
Fixed maturities, Available for sale, Gross Unrealized, Gains	1,457	1,739
Fixed maturities, Available for sale, Gross Unrealized, Losses	(211)	(79)
Common stocks [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity securities, Available for sale, Amortized Cost	1,147	885
Equity securities, Available for sale, Fair Value	1,204	1,087
Equity securities, Available for sale, Gross Unrealized, Gains	151	227
Equity securities, Available for sale, Gross Unrealized, Losses	(94)	(25)
Perpetual preferred stocks [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity securities, Available for sale, Amortized Cost	443	398
Equity securities, Available for sale, Fair Value	454	414
Equity securities, Available for sale, Gross Unrealized, Gains	18	21
Equity securities, Available for sale, Gross Unrealized, Losses	$ (7)	$ (5)

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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