Managed Investment Entities - Selected financial information related to CLOs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Gains (losses) on change in fair value of assets/liabilities:
Assets	$ 132	$ (18)	$ (184)	$ 69
Liabilities	(131)	4	137	(85)
Management fees paid to AFG	3	4	11	11
CLO earnings (losses) attributable to AFG shareholders	13	(5)	(21)	11
Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Investment in CLO tranches at end of period	$ 176	$ 179	$ 176	$ 179	$ 165