Reinsurance (Earned Consolidated Property Casualty Insurance Premiums On Assumed And Ceded Business) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reinsurance [Abstract]
Direct earned premiums	$ 3,520	$ 3,236	$ 3,080
Assumed earned premiums	9	12	10
Ceded earned premiums	(185)	(219)	(166)
Net earned premiums	$ 3,344	$ 3,029	$ 2,924