Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Unearned premiums	$ 119	$ 113
Loss and loss expense reserves	81	66
Deferred international earnings	45	51
Net operating loss on international earnings	26	4
Other	41	39
Deferred tax assets before valuation allowance	312	273
Valuation allowance for international operations	56	41
Deferred tax assets net of valuation allowance	256	232
Deferred tax liabilities:
Investment gains and other, net	1,240	995
Deferred acquisition costs	143	139
Life policy reserves	121	120
Investments	13	23
Other	38	34
Total gross deferred tax liabilities	1,555	1,311
Net deferred income tax liability	$ 1,299	$ 1,079