Long-Term Debt - Narrative (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jun. 03, 2022
Long-term Debt, Fiscal Year Maturity [Abstract]
Scheduled principal payments on debt in next year		$ 0
Scheduled principal payments on debt in year two		0
Scheduled principal payments on debt in year three		0
Scheduled principal payments on debt in year four		0
Scheduled principal payments on debt in year five		0
Scheduled principal payments on debt after year five		1,520,000,000
Principal		1,521,000,000	$ 1,993,000,000
Cash interest payments on long-term debt		89,000,000	92,000,000	$ 83,000,000
Repayments of Long-term Debt		477,000,000	0	150,000,000
AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Revolving credit line		$ 500,000,000
Interest rate description for revolving credit facility		1.00% to 1.875% (currently 1.375%) over LIBOR
Amount borrowed under AFG revolving credit facility		$ 0	0
Repayments of Long-term Debt		$ 477,000,000	0	150,000,000
LIBOR | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on revolving debt facility		1.375%
LIBOR | AFG | Minimum
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on revolving debt facility		1.00%
LIBOR | AFG | Maximum
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on revolving debt facility		1.875%
Senior Notes | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal		$ 846,000,000	1,318,000,000
Senior Notes | 5.25% Senior Notes due April 2030 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal		$ 261,000,000	300,000,000	$ 300,000,000
Interest rate on debt instruments		5.25%		5.25%
Senior Notes, amount of the original debt instrument that was redeemed		$ 39,000,000
Debt Instrument, Repurchase Amount		38,000,000
Senior Notes | 3.50% Senior Notes due August 2026
Long-term Debt, Fiscal Year Maturity [Abstract]
Gain (Loss) on Extinguishment of Debt	$ 6,000,000
Senior Notes | 3.50% Senior Notes due August 2026 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal		$ 0	425,000,000
Interest rate on debt instruments		3.50%
Senior Notes, amount of the original debt instrument that was redeemed		$ 49,000,000			$ 376,000,000
Debt Instrument, Repurchase Amount		51,000,000
Repayments of Long-term Debt	$ 382,000,000
Senior Notes | 4.50% Senior Notes due June 2047 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal		$ 582,000,000	590,000,000
Interest rate on debt instruments		4.50%
Senior Notes, amount of the original debt instrument that was redeemed		$ 8,000,000
Debt Instrument, Repurchase Amount		6,000,000
Subordinated Debt | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal		675,000,000	675,000,000
Subordinated Debt | 4.50% Subordinated Debentures due September 2060 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal		$ 200,000,000	200,000,000	$ 200,000,000
Interest rate on debt instruments		4.50%		4.50%
Subordinated Debt | 6% Subordinated Debentures Due November 2055 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on debt instruments				6.00%
Senior Notes, amount of the original debt instrument that was redeemed				$ 150,000,000
Subordinated Debt | 5.625% Subordinated Debentures due June 2060 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal		$ 150,000,000	150,000,000	$ 150,000,000
Interest rate on debt instruments		5.625%		5.625%
Subordinated Debt | 5.125% Subordinated Debentures due December 2059 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal		$ 200,000,000	200,000,000
Interest rate on debt instruments		5.125%
Subordinated Debt | 5.875% Subordinated Debentures due March 2059 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Principal		$ 125,000,000	$ 125,000,000
Interest rate on debt instruments		5.875%