Property Casualty Loss And Loss Expenses (Consolidated Property Casualty Loss And Loss Expense Reserves) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Insurance [Abstract]
Gross loss and loss expense reserves, January 1	$ 4,438	$ 4,241	$ 4,169
Less reinsurance recoverable	282	299	356
Net loss and loss expense reserves, January 1	4,156	3,942	3,813
Net incurred loss and loss expenses related to:
Current accident year	2,756	2,725	2,448
Prior accident years	(184)	(98)	(147)
Total incurred	2,572	2,627	2,301
Net paid loss and loss expenses related to:
Current accident year	1,152	1,212	1,045
Prior accident years	1,197	1,201	1,127
Total paid	2,349	2,413	2,172
Net loss and loss expense reserves, December 31	4,379	4,156	3,942
Plus reinsurance recoverable	281	282	299
Gross loss and loss expense reserves, December 31	$ 4,660	$ 4,438	$ 4,241