Fair Value Measurements - Narrative (Details) $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($) professional	Dec. 31, 2020 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFG's internal investment professionals \| professional	20
Life contingent annuities	$ 1,120	$ 1,110
Embedded derivatives \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable input surrenders used in Level 3 fair value determination	7.00%
Embedded derivatives \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable input surrenders used in Level 3 fair value determination	22.00%
Fixed-Indexed Annuities (Embedded Derivative) \| Liabilities of discontinued annuity operations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of derivatives in annuity benefits accumulated measured using a discounted cash flow approach	$ 3,950
Fixed-Indexed Annuities (Embedded Derivative), Majority of Future Years \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable input surrenders used in Level 3 fair value determination	8.00%
Fixed-Indexed Annuities (Embedded Derivative), Majority of Future Years \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable input surrenders used in Level 3 fair value determination	11.00%
Level 3 \| Continuing operations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Level 3 assets as a percentage of total assets measured at fair value	5.00%
Percentage of level 3 assets that were priced using non-binding broker quotes	22.00%
Level 3 assets that were priced using non-binding broker quotes	$ 185
Level three assets that were priced by pricing services.	$ 78
Percentage Of Level Three Assets That Were Priced By Pricing Services	9.00%
Internally developed level 3 assets	$ 488
Percentage Of Internally Developed Level Three Assets Compared to Total Level 3 Assets	58.00%

Risk associated with risk of surrenders, expressed as a percentage, used as an input to measure fair value.

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Level 3 assets in which the fair value was developed internally.

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Level Three Asset As Percentage Of Asset Measured At Fair Value.

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Level three assets that were priced by pricing services.

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Level three assets that were priced using non-binding broker quotes.

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Financial liabilities on annuities in the payout phase that are contingent on the survival of the annuitant(s).

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Number of internal investment professionals.

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Percentage Of Internally Developed Level Three Assets Compared to Total Level 3 Assets

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Percentage Of Level Three Assets That Were Priced By Pricing Services

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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