Income Taxes (Significant components of the Company's deferred tax assets and liabilities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred Tax Assets:
Property and casualty claim and claim adjustment expense reserves	$ 352	$ 419
Unearned premium reserves	162	142
Receivables	60	74
Employee benefits	384	323
Life settlement contracts	45	61
Investment valuation differences		3
Net loss and tax credits carried forward	8	25
Other assets	152	159
Gross deferred tax assets	1,163	1,206
Deferred Tax Liabilities:
Investment valuation differences	38
Deferred acquisition costs	238	241
Net unrealized gains	737	513
Other liabilities	57	37
Gross deferred tax liabilities	1,070	791
Net deferred tax asset (liability)	$ 93	$ 415