Managed Investment Entities - Selected financial information related to CLOs (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Gains (losses) on change in fair value of assets/liabilities:
Assets	[1]	$ 0	$ (29)	$ 87	$ (15)
Liabilities	[1]	(2)	27	(89)	10
Management fees paid to AFG		4	4	7	8
CLO earnings (losses) attributable to AFG shareholders	[2]	5	4	16	7
Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Investment in CLO tranches at end of period		$ 191	$ 192	$ 191	$ 192	$ 188

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

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