Acquisitions and Sale of Businesses - Allocation of the purchase price of subsidiary (Details) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
		Nov. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisitions [Line Items]
Total purchase price			$ 36	$ 0	$ 0
Goodwill			$ 207	$ 199	$ 199	$ 199
ABA Insurance Services
Business Acquisitions [Line Items]
Total purchase price		$ 30
Tangible assets acquired		28
Liabilities acquired		26
Net tangible assets acquire, at fair value		2
Excess purchase price over net tangible assets acquired		28
Intangible assets acquired	[1]	25
Deferred tax on intangible assets acquired	[1]	(5)
Goodwill		$ 8

[1] Included in Other assets in AFG’s Balance Sheet.