v3.25.2
Municipal Bond Guarantee Insurance - Schedule of Net Written Premiums (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Written premiums:        
Direct   $ 13.6   $ 24.1
Assumed   0.0   0.0
Gross written premiums   13.6   24.1
Earned premiums:        
Direct   8.5   15.8
Assumed   0.5   1.0
Gross earned premiums   9.0   16.8
Subsidiary - HG Global        
Written premiums:        
Gross written premiums $ 19.2   $ 25.9  
Earned premiums:        
Gross earned premiums 7.1   15.3  
HG Global        
Written premiums:        
Direct 0.0 0.0 0.0 0.0
Assumed 19.2 11.6 25.9 20.5
Gross written premiums 19.2 11.6 25.9 20.5
Earned premiums:        
Direct 0.0 0.0 0.0 0.0
Assumed 7.1 7.5 15.3 14.0
Gross earned premiums $ 7.1 7.5 $ 15.3 14.0
BAM        
Written premiums:        
Direct   13.6   24.1
Assumed   0.0   0.0
Gross written premiums   13.6   24.1
Earned premiums:        
Direct   8.5   15.8
Assumed   0.5   1.0
Gross earned premiums   9.0   16.8
Eliminations        
Written premiums:        
Direct   0.0   0.0
Assumed   (11.6)   (20.5)
Gross written premiums   (11.6)   (20.5)
Earned premiums:        
Direct   0.0   0.0
Assumed   (7.5)   (14.0)
Gross earned premiums   $ (7.5)   $ (14.0)