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Schedule II - Condensed Financial Information of Registrant (Parent Company Only) Schedule II - Condensed Financial Information of Registrant - Income Taxes (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2020 USD ($)
Operating Loss Carryforwards | $ 3,639
Ambac Assurance [Member] |
Operating Loss Generated in Current Year | $ 270
Minimum [Member] |
Operating Loss Carryforwards, Expiration Date | Dec. 31, 2029
Maximum [Member] |
Operating Loss Carryforwards, Expiration Date | Dec. 31, 2040
AFG [Member] |
Operating Loss Carryforwards | $ 1,457
AFG [Member] | Minimum [Member] |
Operating Loss Carryforwards, Expiration Date | Dec. 31, 2029
AFG [Member] | Maximum [Member] |
Operating Loss Carryforwards, Expiration Date | Jan. 01, 2034
Ambac Assurance [Member] | Minimum [Member] |
Operating Loss Carryforwards, Expiration Date | Dec. 31, 2029
Ambac Assurance [Member] | Maximum [Member] |
Operating Loss Carryforwards, Expiration Date | Dec. 31, 2040

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