Reserves For Losses And Loss Expenses (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reserves For Losses And Loss Expenses [Line Items]
Reserve for losses and loss adjustment expenses relating to asbestos and environmental claims, net	$ 36	$ 34
Reserve for losses and loss adjustment expenses relating to asbestos and environmental claims, gross	59	56
Increase (decrease) in net incurred losses and loss expenses relating to asbestos and environmental claims	5	2	1
Net paid losses and loss expenses for asbestos and environmental claims	3	2	3
Workers' compensation discount after effects of ceded reinsurance, amount	$ 837	$ 867	$ 892
Non-Proportional Reinsurance
Reserves For Losses And Loss Expenses [Line Items]
Workers' compensation weighted average discount rate, percent	4.10%
Non-Proportional Reinsurance | Minimum
Reserves For Losses And Loss Expenses [Line Items]
Workers' compensation discount, percent	2.10%
Non-Proportional Reinsurance | Maximum
Reserves For Losses And Loss Expenses [Line Items]
Workers' compensation discount, percent	6.50%
Proportional Reinsurance
Reserves For Losses And Loss Expenses [Line Items]
Workers' compensation discount, percent	2.20%