Managed Investment Entities - Selected financial information related to CLOs (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Gains (losses) on change in fair value of assets/liabilities:
Assets	[1]	$ (18)	$ 20	$ 69	$ 5
Liabilities	[1]	4	(25)	(85)	(15)
Management fees paid to AFG		4	4	11	12
CLO earnings (losses) attributable to AFG shareholders	[2]	(5)	4	11	11
Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Investment in CLO tranches at end of period		$ 179	$ 191	$ 179	$ 191	$ 188

[1] Included in revenues in AFG’s Statement of Earnings.

[2] Included in earnings before income taxes in AFG’s Statement of Earnings.