Reinsurance (Earned Consolidated Property Casualty Insurance Premiums On Assumed And Ceded Business) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct earned premiums	$ 4,857	$ 4,667	$ 4,468
Assumed earned premiums	77	29	12
Ceded earned premiums	(224)	(216)	(237)
Property, Liability and Casualty Insurance Product Line [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct earned premiums	4,567	4,396	4,209
Assumed earned premiums	77	29	12
Ceded earned premiums	(162)	(154)	(176)
Net earned premiums	$ 4,482	$ 4,271	$ 4,045