Long-Term Debt - Narrative (Details) - USD ($)	1 Months Ended	7 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jun. 03, 2022
Long-term Debt, Fiscal Year Maturity [Abstract]
Scheduled principal payments on debt in next year		$ 0	$ 0
Scheduled principal payments on debt in year two		0	0
Scheduled principal payments on debt in year three		0	0
Scheduled principal payments on debt in year four		0	0
Scheduled principal payments on debt in year five		0	0
Scheduled principal payments on debt after year five		$ 1,500,000,000	1,500,000,000
Repayments of long-term debt			21,000,000	$ 477,000,000	$ 0
Cash interest payments on long-term debt			74,000,000	89,000,000	92,000,000
AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Repayments of long-term debt			21,000,000	477,000,000	$ 0
Revolving credit facility term		5 years
Revolving credit line		$ 450,000,000	450,000,000
Amount borrowed under AFG revolving credit facility		$ 0	0	0
SOFR | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on revolving debt facility		1.25%
SOFR | AFG | Minimum
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on revolving debt facility		1.00%
SOFR | AFG | Maximum
Long-term Debt, Fiscal Year Maturity [Abstract]
Interest rate on revolving debt facility		1.75%
Senior Notes | 4.50% Senior Notes due June 2047 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Senior Notes, amount of the original debt instrument that was redeemed		$ 15,000,000	$ 15,000,000	$ 8,000,000
Interest rate on debt instruments		4.50%	4.50%	4.50%
Debt instrument, repurchase amount		$ 13,000,000	$ 13,000,000	$ 6,000,000
Senior Notes | 5.25% Senior Notes due April 2030 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Senior Notes, amount of the original debt instrument that was redeemed		$ 8,000,000	$ 8,000,000	$ 39,000,000
Interest rate on debt instruments		5.25%	5.25%	5.25%
Debt instrument, repurchase amount		$ 8,000,000	$ 8,000,000	$ 38,000,000
Senior Notes | 3.50% Senior Notes due August 2026
Long-term Debt, Fiscal Year Maturity [Abstract]
Gain (loss) on retirement of debt	$ 6,000,000
Senior Notes | 3.50% Senior Notes due August 2026 | AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Senior Notes, amount of the original debt instrument that was redeemed				$ 49,000,000		$ 376,000,000
Interest rate on debt instruments				3.50%
Debt instrument, repurchase amount				$ 51,000,000
Repayments of long-term debt	$ 382,000,000