Goodwill and Other Intangibles - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2015	Jun. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill acquired during period		$ 16			$ 16
Goodwill decrease due to the sale of a subsidiary	$ (2)			$ (2)
Amortizable intangible assets related to property and casualty insurance acquisitions	41		$ 34	41
Accumulated amortization	$ 18		25	18
Amortization of intangible assets			$ 8	$ 8	$ 19
Weighted average useful life of finite-lived intangible assets acquired			4 years
Future amortization of intangibles in next year			$ 8
Future amortization of intangibles in year two			8
Future amortization of intangibles in year three			8
Future amortization of intangibles in year four			8
Future amortization of intangibles after year four			$ 2