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, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred Costs [Roll Forward]
Deferred policy acquisition costs asset at January 1	$ 738	$ 670	$ 637
Capitalized deferred policy acquisition costs	1,095	993	948
Amortized deferred policy acquisition costs	(1,034)	(946)	(913)
Shadow deferred policy acquisition costs	(25)	21	(2)
Deferred policy acquisition costs asset at December 31	774	738	670
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters, Consolidated Property and Casualty Insurance Entity [Member]
Deferred Costs [Roll Forward]
Deferred policy acquisition costs asset at January 1	464	438	408
Capitalized deferred policy acquisition costs	1,034	933	897
Amortized deferred policy acquisition costs	(986)	(907)	(867)
Deferred policy acquisition costs asset at December 31	512	464	438
Life Insurance Product Line [Member]
Deferred Costs [Roll Forward]
Deferred policy acquisition costs asset at January 1	274	232	229
Capitalized deferred policy acquisition costs	61	60	51
Amortized deferred policy acquisition costs	(48)	(39)	(46)
Shadow deferred policy acquisition costs	(25)	21	(2)
Deferred policy acquisition costs asset at December 31	$ 262	$ 274	$ 232