Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Loss and loss expense reserves	$ 123	$ 199
Unearned premiums	100	158
Investments	0	5
Other	27	52
Total gross deferred tax assets	250	414
Deferred tax liabilities:
Unrealized investment gains and other, net	740	907
Deferred acquisition costs	123	195
Life policy reserves	111	162
Investments	10	0
Other	11	15
Total gross deferred tax liabilities	995	1,279
Net deferred income tax liability	$ 745	$ 865