Reinsurance (Reinsurance on premiums - short-duration contracts) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Earned Premiums [Abstract]
Net premiums	$ 1,214		$ 1,426	$ 1,394
Property and casualty [Member]
Written Premiums [Abstract]
Direct written premiums	864	[1]	1,101	1,119
Ceded written premiums	(23)	[1]	(55)	(171)
Total net written premiums	841	[1]	1,046	948
Earned Premiums [Abstract]
Direct earned premiums	841	[1]	1,124	1,107
Ceded earned premiums	(24)	[1]	(94)	(123)
Net premiums	$ 817	[1]	$ 1,030	$ 984

[1] 2019 amounts include AAH premiums as of September 30, 2019 prior to the sale.