Insurance - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Insurance [Line Items]
Carrying value of cash and securities owned by U.S.-based insurance subsidiaries on deposit	$ 1,230
Workers' compensation insurance discount rate	3.50%	3.50%
Workers' compensation insurance discount, which has reduced the liability for unpaid losses and loss adjustment expenses	$ 8	$ 9
Pretax COVID-19 related losses	16	115
Amortization of deferred policy acquisition costs	580	615	$ 721
Dividends on common stock	2,380	336	446
Dividends payments without violating the most restrictive debt covenants, minimum	1,000
Maximum
Insurance [Line Items]
Maximum amount of dividends available to be paid by insurance subsidiaries to AFG without prior approval of regulatory authorities	$ 843
Maximum | Allowance for reinsurance recoverables
Insurance [Line Items]
Net expense reduction against the allowance for losses on reinsurance recoverables			1
Catastrophe Bonds
Insurance [Line Items]
Catastrophe reinsurance coverage, excess retention percentage	94.00%
Catastrophe reinsurance coverage, excess retention amount	$ 325
Catastrophe reinsurance coverage, retention amount	125
Catastrophe reinsurance coverage, annual cost	16
Neon exited lines charge
Insurance [Line Items]
Prior year claims and claims adjustment expense	0	19	7
Other
Insurance [Line Items]
Prior year claims and claims adjustment expense	(279)	(193)	(168)
Other | COVID-19
Insurance [Line Items]
Prior year claims and claims adjustment expense	$ 19
Property and casualty insurance | Other lines
Insurance [Line Items]
Special A&E charges		47	$ 18
Neon Capital Limited | Property and casualty insurance | Other lines
Insurance [Line Items]
Pretax COVID-19 related losses		$ 20