Insurance Claim Reserves (details) - Reserve Detail for Claims and Claim Adjustment Expenses Acquisitions - USD ($) $ in Millions	Dec. 31, 2015	Oct. 01, 2015	Dec. 31, 2014	Dec. 31, 2013	Nov. 01, 2013	Dec. 31, 2012
Liability for claims and claim adjustment expense
Claims and claim adjustment expense reserves	$ 48,295		$ 49,850	$ 50,895
Property casualty [Member]
Liability for claims and claim adjustment expense
Net reserves	39,823		41,036	41,585		$ 40,634
Reinsurance recoverables on unpaid losses	8,449		8,788	9,280		10,254
Claims and claim adjustment expense reserves	$ 48,272		$ 49,824	$ 50,865		$ 50,888
Dominion [Member] | Property casualty [Member]
Liability for claims and claim adjustment expense
Net reserves					$ 1,792
Reinsurance recoverables on unpaid losses					352
Claims and claim adjustment expense reserves					$ 2,144
Travelers Participacoes em Seguros Brasil S.A. [Member] | Property casualty [Member]
Liability for claims and claim adjustment expense
Net reserves		$ 2