Long-Term Debt - Narrative (Details) - USD ($)	1 Months Ended	9 Months Ended
	Jun. 30, 2022	Sep. 30, 2022	Sep. 30, 2021	Jun. 03, 2022	Dec. 31, 2021
Long-term Debt, Fiscal Year Maturity [Abstract]
Scheduled principal payments on debt remainder of fiscal year		$ 0
Scheduled principal payments on debt in year one		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 thereafter		1,560,000,000
Reductions of long-term debt		436,000,000	$ 0
3.50% Senior Notes due August 2026 | Senior Notes
Long-term Debt, Fiscal Year Maturity [Abstract]
Loss on retirement of debt, including make-whole call premium	$ (6,000,000)
AFG
Long-term Debt, Fiscal Year Maturity [Abstract]
Revolving credit line		500,000,000
Amount borrowed under revolving credit facility		$ 0			$ 0
AFG | 3.50% Senior Notes due August 2026 | Senior Notes
Long-term Debt, Fiscal Year Maturity [Abstract]
Face amount of debt repurchased	49,000,000			$ 376,000,000
Interest rate on debt instruments		3.50%		3.50%
Amount of debt repurchased	51,000,000
Reductions of long-term debt	$ 382,000,000
AFG | 4.50% Senior Notes due June 2047 | Senior Notes
Long-term Debt, Fiscal Year Maturity [Abstract]
Face amount of debt repurchased		$ 4,000,000
Interest rate on debt instruments		4.50%
Amount of debt repurchased		$ 3,000,000
AFG | 5.25% Senior Notes due April 2030 | Senior Notes
Long-term Debt, Fiscal Year Maturity [Abstract]
Face amount of debt repurchased		$ 5,000,000
Interest rate on debt instruments		5.25%
Amount of debt repurchased		$ 5,000,000
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%