Goodwill (details) - Other Intangible Assets - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Nov. 01, 2013	Apr. 01, 2004
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount	$ 210	$ 669
Intangible assets subject to amortization, accumulated amortization	148	582
Intangible assets subject to amortization, net	62	87
Amortization expense for other intangible assets	26	46	$ 46
Estimated intangible asset amortization expense, 2016	11
Estimated intangible asset amortization expense, 2017	9
Estimated intangible asset amortization expense, 2018	8
Estimated intangible asset amortization expense, 2019	6
Estimated intangible asset amortization expense, 2020	$ 5
Customer-related [Member]
Other intangible assets by major asset class
Intangible assets subject to amortization, gross carrying amount		460
Intangible assets subject to amortization, accumulated amortization		$ 446
Dominion [Member] | Fair value adjustment on claims and claim adjustment expense reserves and reinsurance recoverables [Member]
Other intangible assets by major asset class
Intangible assets acquired				$ 5
Dominion [Member] | Contract-related [Member]
Other intangible assets by major asset class
Intangible assets acquired				$ 5
Travelers Property Casualty Corp. [Member] | Fair value adjustment on claims and claim adjustment expense reserves and reinsurance recoverables [Member]
Other intangible assets by major asset class
Intangible assets acquired					$ 191