Investments (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	$ 31,565	$ 29,074
Available for sale (AFS) fixed maturities	32,284	30,734
Equity securities, Available for sale, Amortized Cost	1,469	1,283
Equity securities, Available for sale, Fair Value	1,553	1,501
U.S. Government and government agencies [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	305	347
Available for sale (AFS) fixed maturities	307	353
Fixed maturities, Available for sale, Gross Unrealized, Gains	5	8
Fixed maturities, Available for sale, Gross Unrealized, Losses	(3)	(2)
States, municipalities and political subdivisions [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	6,642	6,393
Available for sale (AFS) fixed maturities	6,856	6,747
Fixed maturities, Available for sale, Gross Unrealized, Gains	249	364
Fixed maturities, Available for sale, Gross Unrealized, Losses	(35)	(10)
Foreign government [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	147	184
Available for sale (AFS) fixed maturities	154	194
Fixed maturities, Available for sale, Gross Unrealized, Gains	7	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	3,236	4,046
Available for sale (AFS) fixed maturities	3,529	4,442
Fixed maturities, Available for sale, Gross Unrealized, Gains	308	411
Fixed maturities, Available for sale, Gross Unrealized, Losses	(15)	(15)
Commercial Mortgage Backed Securities [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	2,111	2,294
Available for sale (AFS) fixed maturities	2,187	2,451
Fixed maturities, Available for sale, Gross Unrealized, Gains	77	158
Fixed maturities, Available for sale, Gross Unrealized, Losses	(1)	(1)
Asset-backed Securities [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	4,961	3,872
Available for sale (AFS) fixed maturities	4,934	3,887
Fixed maturities, Available for sale, Gross Unrealized, Gains	25	37
Fixed maturities, Available for sale, Gross Unrealized, Losses	(52)	(22)
All other corporate [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	14,163	11,938
Available for sale (AFS) fixed maturities	14,317	12,660
Fixed maturities, Available for sale, Gross Unrealized, Gains	422	751
Fixed maturities, Available for sale, Gross Unrealized, Losses	(268)	(29)
Fixed maturities [Member]
Available for sale fixed maturities and equity securities
Fixed maturities, Available for sale, Amortized Cost	31,565	29,074
Available for sale (AFS) fixed maturities	32,284	30,734
Fixed maturities, Available for sale, Gross Unrealized, Gains	1,093	1,739
Fixed maturities, Available for sale, Gross Unrealized, Losses	(374)	(79)
Common stocks [Member]
Available for sale fixed maturities and equity securities
Equity securities, Available for sale, Amortized Cost	1,051	885
Equity securities, Available for sale, Fair Value	1,118	1,087
Equity securities, Available for sale, Gross Unrealized, Gains	146	227
Equity securities, Available for sale, Gross Unrealized, Losses	(79)	(25)
Perpetual preferred stocks [Member]
Available for sale fixed maturities and equity securities
Equity securities, Available for sale, Amortized Cost	418	398
Equity securities, Available for sale, Fair Value	435	414
Equity securities, Available for sale, Gross Unrealized, Gains	23	21
Equity securities, Available for sale, Gross Unrealized, Losses	$ (6)	$ (5)