Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:
Loss and loss expense reserves	$ 202	$ 201
Unearned premiums	124	113
Investments	31	36
Other	39	46
Total	396	396
Deferred tax liabilities:
Unrealized investment gains and other	605	481
Deferred acquisition costs	163	156
Life policy reserves	65	42
Other	16	20
Total	849	699
Net deferred tax liability	$ 453	$ 303