Income Taxes (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2010
Reconciliation of the change in the amount of unrecognized tax benefits
Balance at beginning of period		$ 25	$ 25	$ 25
Increase for tax positions taken in a prior year		1
Decrease for settlements		(26)
Balance at end of period			25	25
Unrecognized tax benefits interest accrued	0	0
Penalties accrued	0
Deferred assets
Unearned premium reserves	763	722
Pension	254
Discount on loss reserves	210	238
Accrued compensation	206	226
Other postretirement benefits	138	105
Difference in tax bases of invested assets	64	223
Sale of subsidiary	20	196
Other assets	118	96
Total deferred assets	1,773	1,806
Deferred liabilities
DAC	(1,076)	(1,077)
Unrealized net capital gains	(994)	(849)
Life and annuity reserves	(192)	(206)
Pension		(136)
Other liabilities	(226)	(324)
Total deferred liabilities	(2,488)	(2,592)
Net deferred liability before classification as held for sale	(715)	(786)
Deferred taxes classified as held for sale		(151)
Net deferred liability	(715)	(635)
Net operating loss carryforward	94
Components of income tax expense (benefit)
Current	1,123	869	295
Deferred	263	247	705
Total income tax expense	1,386	1,116	1,000
Income tax paid	1,070	500	280
Current income tax payable	$ 158	$ 203
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation
Statutory federal income tax rate (as a percent)	35.00%	35.00%	35.00%
Tax-exempt income (as a percent)	(0.90%)	(1.80%)	(3.00%)
Tax credits (as a percent)	(0.70%)	(2.20%)	(1.40%)
Sale of subsidiary (as a percent)	(0.90%)	2.00%
Other (as a percent)	0.20%	(0.10%)	(0.30%)
Effective income tax rate (as a percent)	32.70%	32.90%	30.30%