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Municipal Bond Guarantee Insurance - Schedule of Municipal Guarantee Insurance Contracts, Premium Received Over Contract Period (Details) - Variable Interest Entity, Primary Beneficiary - Build America Mutual Assurance Company $ in Millions | Mar. 31, 2024 USD ($)
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Guarantor Obligations [Line Items] |
April 1, 2024 - December 31, 2024 | $ 22.4
January 1, 2025 - March 31, 2025 | 7.2
April 1, 2025 - June 30, 2025 | 7.2
July 1, 2025 - September 30, 2025 | 7.0
October 1, 2025 - December 31, 2025 | 6.9
Total 2025 | 28.3
2026 | 26.6
2027 | 24.9
2028 | 23.1
2029 | 21.4
2030 and thereafter | 181.8
Total gross unearned insurance premiums | $ 328.5

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