Managed Investment Entities - Selected financial information related to CLOs (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Gains (losses) on change in fair value of assets/liabilities:
Assets	[1]	$ (8)	$ 60	$ (12)	$ 107
Liabilities	[1]	9	(49)	24	(98)
Management fees paid to AFG		5	4	14	12
CLO earnings (losses) attributable to AFG shareholders	[2]	5	17	16	29
Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Investment in CLO tranches at end of period		$ 261	$ 245	$ 261	$ 245	$ 216

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

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