Deferred Policy Acquisition Costs (Deferred Policy Acquisition Costs And Asset Reconciliation Including The Amortized Deferred Policy Acquisition Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred Costs [Roll Forward]
Deferred policy acquisition costs asset at January 1	$ 578	$ 565	$ 470
Capitalized deferred policy acquisition costs	846	827	802
Amortized deferred policy acquisition costs	(829)	(807)	(758)
Amortized shadow deferred policy acquisition costs	21	(7)	51
Deferred policy acquisition costs asset at December 31	616	578	565
Property Casualty Insurance Segment [Member]
Deferred Costs [Roll Forward]
Deferred policy acquisition costs asset at January 1	379	366	337
Capitalized deferred policy acquisition costs	801	783	756
Amortized deferred policy acquisition costs	(792)	(770)	(727)
Deferred policy acquisition costs asset at December 31	388	379	366
Life Insurance Product Line [Member]
Deferred Costs [Roll Forward]
Deferred policy acquisition costs asset at January 1	199	199	133
Capitalized deferred policy acquisition costs	45	44	46
Amortized deferred policy acquisition costs	(37)	(37)	(31)
Amortized shadow deferred policy acquisition costs	21	(7)	51
Deferred policy acquisition costs asset at December 31	$ 228	$ 199	$ 199