Managed Investment Entities - Selected financial information related to CLOs (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Gains (losses) on change in fair value of assets/liabilities:
Assets	[1]	$ 14	$ 5
Liabilities	[1]	(17)	(5)
Management fees paid to AFG		4	4
CLO earnings (losses) attributable to AFG shareholders	[2]	3	6
Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Investment in CLO tranches at end of period		$ 221	$ 230	$ 215

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

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