Managed Investment Entities - Selected financial information related to CLOs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Gains (losses) on change in fair value of assets/liabilities:
Assets	$ 46	$ (679)
Liabilities	(44)	666
Management fees paid to AFG	4	4
CLO earnings (losses) attributable to AFG shareholders	18	(36)
Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Investment in CLO tranches	181	161	$ 200
Variable interest entity, primary beneficiary | Continuing operations
Variable Interest Entity [Line Items]
Investment in CLO tranches	57	40
Gains (losses) on change in fair value of assets/liabilities:
CLO earnings (losses) attributable to AFG shareholders	5	(11)
Variable interest entity, primary beneficiary | Net earnings (loss) from discontinued operations | Annuity subsidiaries
Variable Interest Entity [Line Items]
Investment in CLO tranches	124	121
Gains (losses) on change in fair value of assets/liabilities:
CLO earnings (losses) attributable to AFG shareholders	$ 13	$ (25)