Property Casualty Loss And Loss Expenses (Consolidated Property Casualty Loss And Loss Expense Reserves) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Insurance [Abstract]
Gross loss and loss expense reserves, January 1	$ 4,241	$ 4,169	$ 4,280
Less reinsurance recoverable	299	356	375
Net loss and loss expense reserves, January 1	3,942	3,813	3,905
Net incurred loss and loss expenses related to:
Current accident year	2,725	2,448	2,533
Prior accident years	(98)	(147)	(396)
Total incurred	2,627	2,301	2,137
Net paid loss and loss expenses related to:
Current accident year	1,212	1,045	1,123
Prior accident years	1,201	1,127	1,106
Total paid	2,413	2,172	2,229
Net loss and loss expense reserves, December 31	4,156	3,942	3,813
Plus reinsurance recoverable	282	299	356
Gross loss and loss expense reserves, December 31	$ 4,438	$ 4,241	$ 4,169