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Insurance - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Dec. 31, 2020 | Sep. 30, 2020 | Jun. 30, 2020 | Mar. 31, 2020 | Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Jun. 30, 2020 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Carrying value of cash and securities owned by U.S.-based insurance subsidiaries on deposit | $ 1,120 |  |  |  |  |  |  |  |  | $ 1,120 |  |
Undrawn letters of credit | 308 |  |  |  |  |  |  |  |  | 308 |  |
Undrawn letters of credit, collateralized | 0 |  |  |  |  |  |  |  |  | $ 0 |  |
Workers' compensation insurance discount rate |  |  |  |  |  |  |  |  |  | 3.50% | 4.50% |
Workers' compensation insurance discount, which has reduced the liability for unpaid losses and loss adjustment expenses | 9 |  |  |  | $ 12 |  |  |  |  | $ 9 | $ 12 |
Pretax COVID-19 related losses |  |  | $ 105 | $ 10 |  |  |  |  |  | 115 |  |
Prior year claims and claims adjustment expense | 8 | $ 0 | $ 77 | $ 42 | 45 | $ 12 | $ 41 | $ 45 |  | 127 | 143 |
Long-term care insurance reserves, net of reinsurance recoverables | 52 |  |  |  | 46 |  |  |  |  | 52 | 46 |
Dividends on common stock |  |  |  |  |  |  |  |  |  | (336) | (446) | $ (397)
Dividends payments without violating the most restrictive debt covenants, minimum | 2,000 |  |  |  |  |  |  |  |  | 2,000 |  |
Catastrophe reinsurance coverage, excess retention amount |  |  |  |  |  |  |  |  |  | 50 |  |
Catastrophe reinsurance coverage, retention amount |  |  |  |  |  |  |  |  |  | 100 |  |
Ceded annuity receipts |  |  |  |  |  |  |  |  |  | 492 | 0 | 0
Ceded annuity surrenders, benefits and withdrawals |  |  |  |  |  |  |  |  |  | 206 | 0 | 0
Aggregate guaranteed minimum death benefit value on variable annuity polices in force | 11 |  |  |  | 13 |  |  |  |  | 11 | 13 |
Retained Earnings |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Dividends on common stock |  |  |  |  |  |  |  |  |  | (336) | (446) | (397)
Allowance for reinsurance recoverables |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Net expense reduction against the allowance for losses on reinsurance recoverables |  |  |  |  |  |  |  |  |  |  |  | 2
Maximum |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Maximum amount of dividends available to be paid by insurance subsidiaries to AFG without prior approval of regulatory authorities | 705 |  |  |  |  |  |  |  |  | $ 705 |  |
Maximum | Allowance for reinsurance recoverables |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Net expense reduction against the allowance for losses on reinsurance recoverables |  |  |  |  |  |  |  |  |  |  | 1 |
Catastrophe Bonds |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Catastrophe reinsurance coverage, excess retention percentage |  |  |  |  |  |  |  |  |  | 95.00% |  |
Catastrophe reinsurance coverage, excess retention amount |  |  |  |  |  |  |  |  |  | $ 200 |  |
Catastrophe reinsurance coverage, retention amount |  |  |  |  |  |  |  |  |  | 109 |  |
Catastrophe reinsurance coverage, annual cost |  |  |  |  |  |  |  |  |  | 11 |  |
Life insurance |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Life insurance in force, ceded premiums | 5,420 |  |  |  | 6,230 |  |  |  |  | 5,420 | 6,230 |
Life insurance in force, direct premiums | 8,330 |  |  |  | 9,530 |  |  |  |  | 8,330 | 9,530 |
Reinsurance ceded |  |  |  |  |  |  |  |  |  | 19 | 20 | 22
Reinsurance recoveries |  |  |  |  |  |  |  |  |  | 28 | 32 | 38
Variable annuities | Maximum |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Death benefits paid in excess of the variable annuity account balances |  |  |  |  |  |  |  |  |  | 1 | 1 | 1
Neon exited lines charge |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Prior year claims and claims adjustment expense |  |  |  |  |  |  |  |  |  | 19 | 7 | 0
Property and casualty insurance | Other lines |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Special A&E charges |  | $ 47 |  |  |  | $ 18 |  |  |  | 47 | 18 | 18
Neon Capital Limited | Property and casualty insurance | Other lines |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Pretax COVID-19 related losses |  |  |  |  |  |  |  |  | $ 20 | 20 |  |
Great American Life Insurance Company |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Investment in Federal Home Loan Bank capital stock | 56 |  |  |  |  |  |  |  |  | 56 |  |
Proceeds advanced from Federal Home Loan |  |  |  |  |  |  |  |  |  | 200 |  |
Repayments of advances from Federal Home Loan Bank |  |  |  |  |  |  |  |  |  | 165 |  |
Advances from Federal Home Loan Bank | 1,130 |  |  |  | 1,100 |  |  |  |  | 1,130 | 1,100 |
Repayments of advances from Federal Home Loan Bank due in next twelve months | 931 |  |  |  |  |  |  |  |  | 931 |  |
Repayments of advances from Federal Home Loan Bank due in year five | 200 |  |  |  |  |  |  |  |  | 200 |  |
Fair value of fixed maturity investments held as collateral by the Federal Home Loan Bank | $ 1,370 |  |  |  |  |  |  |  |  | 1,370 |  |
Interest on advances from Federal Home Loan Bank |  |  |  |  |  |  |  |  |  | $ 11 | 27 | $ 20
Quota share coinsurance percentage |  |  |  |  |  |  |  |  |  | 0.50 |  |
Inforce Annuity Business, Ceded, Percent of Total Inforce | 15.00% |  |  |  |  |  |  |  |  |  |  |
Deferred Loss on Ceded Reserves | $ 180 |  |  |  |  |  |  |  |  |  |  |
Amortization of deferred loss on reinsurance | 11 |  |  |  |  |  |  |  |  |  |  |
Ceded annuity receipts |  |  |  |  |  |  |  |  |  | $ 492 |  |
Ceded annuity surrenders, benefits and withdrawals |  |  |  |  |  |  |  |  |  | 206 |  |
Commission and expense allowances received from reinsurance contracts |  |  |  |  |  |  |  |  |  | 39 |  |
Amount of annuity benefits expense reduction from reinsurance contracts |  |  |  |  |  |  |  |  |  | $ 46 |  |
Great American Life Insurance Company | Block Reinsurance |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Ceded Inforce Annuity Business | $ 5,960 |  |  |  |  |  |  |  |  |  |  |
Great American Life Insurance Company | Minimum |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Interest rates on Federal Home Loan Bank advances | 0.31% |  |  |  |  |  |  |  |  | 0.31% |  |
Expected Life of Ceded Reserves | 7 years |  |  |  |  |  |  |  |  |  |  |
Great American Life Insurance Company | Maximum |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Interest rates on Federal Home Loan Bank advances | 1.35% |  |  |  |  |  |  |  |  | 1.35% |  |
Expected Life of Ceded Reserves | 10 years |  |  |  |  |  |  |  |  |  |  |
Great American Life Insurance Company | Average |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Interest rates on Federal Home Loan Bank advances | 0.53% |  |  |  |  |  |  |  |  | 0.53% |  |
Great American Life Insurance Company | FHLB, advances, refinanced terms |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Advances from Federal Home Loan Bank |  |  |  |  | $ 610 |  |  |  |  |  | 610 |
Great American Life Insurance Company | Life insurance |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Increases in statutory surplus from reinsurance treaty |  |  |  |  |  |  |  |  |  | $ 139 | $ 124 |

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