Reinsurance (Incurred Consolidated Property Casualty Insurance Loss And Loss Expenses On Assumed And Ceded Business) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net incurred loss and loss expenses	$ 3,107	$ 2,808	$ 2,856
Property, Liability and Casualty Insurance Product Line [Member]
Direct incurred loss and loss expenses	2,874	2,596	2,661
Assumed incurred loss and loss expenses	43	12	6
Ceded incurred loss and loss expenses	(56)	(36)	(40)
Net incurred loss and loss expenses	$ 2,861	$ 2,572	$ 2,627