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Municipal Bond Guarantee Insurance - Schedule of Net Written Premiums (Details) - Financial Guarantee (HG Global/BAM) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Written premiums:
Direct	$ 13.6	$ 11.6	$ 24.1	$ 20.8
Assumed	0.0	0.0	0.0	0.0
Gross written premiums	13.6	11.6	24.1	20.8
Earned premiums:
Direct	8.5	7.0	15.8	14.0
Assumed	0.5	0.7	1.0	1.4
Gross earned premiums	$ 9.0	$ 7.7	$ 16.8	$ 15.4

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