v3.25.2
Long-Term Debt - Schedule of long-term debt (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Summary of Carrying value of long-term debt    
Principal $ 1,498 $ 1,498
Discount and Issue Costs (22) (23)
Carrying Value 1,476 1,475
Senior Notes | AFG    
Summary of Carrying value of long-term debt    
Principal 823 823
Discount and Issue Costs (4) (5)
Carrying Value $ 819 818
Senior Notes | 4.50% Senior Notes due June 2047 | AFG    
Debt Instrument [Line Items]    
Interest rate on debt instruments 4.50%  
Summary of Carrying value of long-term debt    
Principal $ 567 567
Discount and Issue Costs (1) (1)
Carrying Value $ 566 566
Senior Notes | 5.25% Senior Notes due April 2030 | AFG    
Debt Instrument [Line Items]    
Interest rate on debt instruments 5.25%  
Summary of Carrying value of long-term debt    
Principal $ 253 253
Discount and Issue Costs (3) (4)
Carrying Value 250 249
Senior Notes | Other | AFG    
Summary of Carrying value of long-term debt    
Principal 3 3
Discount and Issue Costs 0 0
Carrying Value 3 3
Subordinated Debentures | AFG    
Summary of Carrying value of long-term debt    
Principal 675 675
Discount and Issue Costs (18) (18)
Carrying Value $ 657 657
Subordinated Debentures | 4.50% Subordinated Debentures due September 2060 | AFG    
Debt Instrument [Line Items]    
Interest rate on debt instruments 4.50%  
Summary of Carrying value of long-term debt    
Principal $ 200 200
Discount and Issue Costs (5) (5)
Carrying Value $ 195 195
Subordinated Debentures | 5.125% Subordinated Debentures due December 2059 | AFG    
Debt Instrument [Line Items]    
Interest rate on debt instruments 5.125%  
Summary of Carrying value of long-term debt    
Principal $ 200 200
Discount and Issue Costs (5) (5)
Carrying Value $ 195 195
Subordinated Debentures | 5.625% Subordinated Debentures due June 2060 | AFG    
Debt Instrument [Line Items]    
Interest rate on debt instruments 5.625%  
Summary of Carrying value of long-term debt    
Principal $ 150 150
Discount and Issue Costs (4) (4)
Carrying Value $ 146 146
Subordinated Debentures | 5.875% Subordinated Debentures due March 2059 | AFG    
Debt Instrument [Line Items]    
Interest rate on debt instruments 5.875%  
Summary of Carrying value of long-term debt    
Principal $ 125 125
Discount and Issue Costs (4) (4)
Carrying Value $ 121 $ 121