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Municipal Bond Guarantee - Schedule of Municipal Guarantee Insurance Contracts, Premium Received Over Contract Period (Details) - Variable Interest Entity, Primary Beneficiary - Build America Mutual Assurance Company $ in Millions | Dec. 31, 2023 USD ($)
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Guarantor Obligations [Line Items] |
January 1, 2024 - March 31, 2024 | $ 7.5
April 1, 2024 - June 30, 2024 | 7.5
July 1, 2024 - September 30, 2024 | 7.3
October 1, 2024 - December 31, 2024 | 7.2
Total | 29.5
2025 | 27.7
2026 | 26.0
2027 | 24.4
2028 | 22.6
2029 and thereafter | 195.6
Total gross unearned insurance premiums | $ 325.8

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