Municipal Bond Guarantee Reinsurance - Schedule of Net Written Premiums (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Written premiums:
Direct			$ 24.1	$ 58.6
Assumed			31.9	0.0
Gross written premiums			56.0	58.6
Earned premiums:
Direct			15.8	28.7
Assumed Premiums Earned			15.9	2.5
Gross earned premiums			31.7	31.2
Direct written premiums			56.0	58.6
Gross earned premiums			31.7	31.2
HG Global
Written premiums:
Direct		$ 0.0	0.0	0.0
Assumed		61.4	52.4	50.1
Gross written premiums		61.4	52.4	50.1
Earned premiums:
Direct		0.0	0.0	0.0
Assumed Premiums Earned		30.8	28.9	26.0
Gross earned premiums		30.8	28.9	26.0
Direct written premiums		61.4	52.4	50.1
Gross earned premiums		$ 30.8	28.9	26.0
Ceded premiums written	$ (20.5)			(50.1)
Ceded to Other Companies	$ (14.0)			(26.0)
BAM
Written premiums:
Direct			24.1	58.6
Assumed			0.0	0.0
Gross written premiums			24.1	58.6
Earned premiums:
Direct			15.8	28.7
Assumed Premiums Earned			1.0	2.5
Gross earned premiums			16.8	31.2
Direct written premiums			24.1	58.6
Gross earned premiums			16.8	31.2
Eliminations
Written premiums:
Direct			0.0	0.0
Assumed			(20.5)	(50.1)
Gross written premiums			(20.5)	(50.1)
Earned premiums:
Direct			0.0	0.0
Assumed Premiums Earned			(14.0)	(26.0)
Gross earned premiums			(14.0)	(26.0)
Direct written premiums			(20.5)	(50.1)
Gross earned premiums			$ (14.0)	$ (26.0)