Reinsurance (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts, life insurance in force	$ 85,015	$ 81,467	$ 77,691
Gross amounts	4,151	3,755	3,456
Ceded amounts to other companies, life insurance in force	36,952	36,340	35,690
Ceded amounts to other companies	260	242	274
Assumed amounts from other companies, life insurance in force	0	0	1
Assumed amounts from other companies	11	9	12
Net amounts, life insurance in force	48,063	45,126	42,001
Net amounts	3,902	3,522	3,194
Percentage of amounts assumed to net, life insurance in force	0.00%	0.00%	0.00%
Percentage of amounts assumed to net	0.50%	0.30%	0.40%
Commercial Lines [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts	2,777	2,524	2,348
Ceded amounts to other companies	151	149	162
Assumed amounts from other companies	10	8	11
Net amounts	2,636	2,383	2,197
Percentage of amounts assumed to net	0.40%	0.30%	0.50%
Personal Lines [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts	1,002	897	812
Ceded amounts to other companies	42	30	51
Assumed amounts from other companies	1	1	1
Net amounts	961	868	762
Percentage of amounts assumed to net	0.10%	0.10%	0.20%
Excess And Surplus Lines Insurance [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts	124	99	76
Ceded amounts to other companies	8	6	6
Assumed amounts from other companies	0	0	0
Net amounts	116	93	70
Percentage of amounts assumed to net	0.00%	0.00%	0.00%
Property, Liability And Casualty Insurance Segment [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts	3,903	3,520	3,236
Ceded amounts to other companies	201	185	219
Assumed amounts from other companies	11	9	12
Net amounts	3,713	3,344	3,029
Percentage of amounts assumed to net	0.50%	0.30%	0.40%
Life Insurance Segment [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amounts	248	235	220
Ceded amounts to other companies	59	57	55
Assumed amounts from other companies	0	0	0
Net amounts	$ 189	$ 178	$ 165
Percentage of amounts assumed to net	0.00%	0.00%	0.00%