Investments (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
U.S. Government and government agencies [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	$ 316	$ 310
Fair Value	321	314
Gross Unrealized, Gains	8	7
Gross Unrealized, Losses	(3)	(3)
States, municipalities and political subdivisions [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	5,579	5,360
Fair Value	5,723	5,372
Gross Unrealized, Gains	214	156
Gross Unrealized, Losses	(70)	(144)
Foreign government [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	184	198
Fair Value	193	208
Gross Unrealized, Gains	9	10
Gross Unrealized, Losses	0	0
Residential Mortgage Backed Securities [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	4,193	3,947
Fair Value	4,581	4,310
Gross Unrealized, Gains	412	391
Gross Unrealized, Losses	(24)	(28)
Commercial Mortgage Backed Securities [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	2,435	2,535
Fair Value	2,619	2,724
Gross Unrealized, Gains	185	192
Gross Unrealized, Losses	(1)	(3)
Asset-backed Securities [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	2,737	2,477
Fair Value	2,760	2,493
Gross Unrealized, Gains	39	35
Gross Unrealized, Losses	(16)	(19)
All other corporate [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	10,540	10,539
Fair Value	11,193	11,035
Gross Unrealized, Gains	702	604
Gross Unrealized, Losses	(49)	(108)
Fixed maturities [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	25,984	25,366
Fair Value	27,390	26,456
Gross Unrealized, Gains	1,569	1,395
Gross Unrealized, Losses	(163)	(305)
Common stocks [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	801	721
Fair Value	996	914
Gross Unrealized, Gains	207	209
Gross Unrealized, Losses	(12)	(16)
Perpetual preferred stocks [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	291	266
Fair Value	301	265
Gross Unrealized, Gains	15	9
Gross Unrealized, Losses	$ (5)	$ (10)