Fair Value Measurements - Narrative (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) professional	Dec. 31, 2021 USD ($)	Dec. 06, 2021 USD ($)
Fair Value Measurements (Textual) [Abstract]
AFG's internal investment professionals | professional	20
Level 3 assets as a percentage of total assets measured at fair value	7.00%
Percentage of level 3 assets that were priced using non-binding broker quotes	12.00%
Level 3 assets that were priced using non-binding broker quotes	$ 126,000,000
Level 3 assets that were priced by pricing services.	$ 47,000,000
Percentage of Level 3 assets that were priced using a discounted cash flow approach	62.00%
Level 3 assets that were priced using a discounted cash flow approach	$ 420,000,000
Percentage of equity securities in Level 3 priced using broker quotes and internal models	24.00%
Equity securities in Level 3 priced using broker quotes and internal models	$ 164,000,000
Contingent consideration - acquisitions
Fair Value Measurements (Textual) [Abstract]
Contingent consideration	25,000,000	$ 23,000,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	0
Verikai, Inc.
Fair Value Measurements (Textual) [Abstract]
Contingent consideration			$ 23,000,000
Verikai, Inc. | Contingent consideration - acquisitions
Fair Value Measurements (Textual) [Abstract]
Contingent consideration	23,000,000
Level 3
Fair Value Measurements (Textual) [Abstract]
Internally developed Level 3 assets	$ 674,000,000
Percentage of internally developed Level 3 assets compared to total Level 3 assets	61.00%
Level 3 | Contingent consideration - acquisitions
Fair Value Measurements (Textual) [Abstract]
Contingent consideration	$ 25,000,000	$ 23,000,000
Level 3 | Continuing operations
Fair Value Measurements (Textual) [Abstract]
Percentage of Level 3 assets that were priced by pricing services	4.00%
Percentage of equity investments in Level 3 assets that do not qualify for equity accounting	23.00%
Equity investments in Level 3 assets that do not qualify for equity accounting	$ 255,000,000