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Municipal Bond Guarantee - Schedule of Net Written Premiums (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |
Gross earned premiums | $ 6.2 | $ 5.2 | $ 17.2 | $ 13.7
HG/BAM |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |
Direct written premiums | 14.4 | 10.2 | 45.5 | 30.6
Assumed written premiums | 0.0 | 10.6 | 0.1 | 10.6
Gross written premiums |  | 20.8 | 45.6 | 41.2
Direct premiums earned | 5.3 | 4.4 | 14.5 | 11.9
Assumed premiums earned | 0.9 | 0.8 | 2.7 | 1.8
Gross earned premiums | $ 6.2 | $ 5.2 | $ 17.2 | $ 13.7

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