Municipal Bond Guarantee Insurance - Schedule of Net Written Premiums (Details) - Financial Guarantee (HG Global/BAM) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Written premiums:
Direct	$ 10.5	$ 9.2
Assumed	0.0	0.0
Gross written premiums	10.5	9.2
Earned premiums:
Direct	7.3	7.0
Assumed	0.5	0.7
Gross earned premiums	$ 7.8	$ 7.7

Amount of earned premiums assumed from other entities.

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Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

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Amount of direct and assumed premiums written.

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