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Municipal Bond Guarantee - Schedule of Net Written Premiums (Details) - HG/BAM - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |
Direct written premiums | $ 10.2 | $ 3.9 | $ 30.6 | $ 28.9
Assumed written premiums | 10.6 | 0.0 | 10.6 | 0.0
Gross written premiums | 20.8 | 3.9 | 41.2 | 28.9
Direct premiums earned | 4.4 | 3.3 | 11.9 | 9.7
Assumed premiums earned | 0.8 | 0.0 | 1.8 | 0.0
Gross earned premiums | $ 5.2 | $ 3.3 | $ 13.7 | $ 9.7

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