Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Loss and loss expense reserves	$ 191	$ 197
Unearned premiums	151	145
Investments	25	16
Other	42	41
Total gross deferred tax assets	409	399
Deferred tax liabilities:
Unrealized investment gains, net	719	937
Deferred acquisition costs	187	183
Life policy reserves	137	110
Other	4	9
Total gross deferred tax liabilities	1,047	1,239
Net deferred income tax liability	$ 638	$ 840