v3.26.1
Shareholders' equity - Narrative (Details) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended 6 Months Ended
Feb. 26, 2026
Jan. 29, 2026
Feb. 27, 2025
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Class of Stock [Line Items]                
Common shares authorized (in shares)       300,000,000   300,000,000    
Common shares, par value (in dollars per share)       $ 0.10   $ 0.10    
Dividends paid to common shareholders           $ 0.0 $ 0.0  
Dividends paid to preference shareholders           2.6 $ 8.0  
Stock repurchase program, remaining authorized amount       $ 101.1   $ 101.1    
Common shares repurchased and retired (in shares)       2,237,688   3,290,298    
Common shares repurchased and retired       $ 51.5   $ 73.3    
Shares acquired price (in dollars per share)       $ 23.00   $ 22.29    
Commissions cost per share (in dollars per share)       $ 0.03   $ 0.03    
Director                
Class of Stock [Line Items]                
Common shares repurchased and retired (in shares)     500,000          
Shares acquired price (in dollars per share)     $ 14.00          
CMIG Securities Purchase Agreement                
Class of Stock [Line Items]                
Shares acquired price (in dollars per share)             $ 14.25  
Common Stock                
Class of Stock [Line Items]                
Common shares repurchased and retired (in shares)           3,290,298 500,000  
Common shares repurchased and retired       $ 0.2 $ 0.0 $ 0.3 $ 0.1  
Common Stock | CMIG Securities Purchase Agreement                
Class of Stock [Line Items]                
Common shares repurchased and retired (in shares)             45,720,732  
Preference shares                
Class of Stock [Line Items]                
Preference shares, shares authorized (in shares)       30,000,000   30,000,000    
Preference shares, par value (in dollars per share)       $ 0.10   $ 0.10    
Series B preference shares                
Class of Stock [Line Items]                
Preference shares, shares authorized (in shares)       8,000,000   8,000,000   8,000,000
Preference shares, par value (in dollars per share)   $ 0.10   $ 0.10   $ 0.10   $ 0.10
Preference shares, shares outstanding (in shares)   8,000,000            
Dividend rate   8.00%            
Stock redeemed (in shares) 8,000,000              
Preferred stock, redemption price (in dollars per share) $ 25.00              
Preferred stock, accrued cumulative dividend (in dollars per share) $ 0.49              
Aggregated redemption price       $ 203.9   $ 203.9    
Dividends paid to preference shareholders       $ 2.6 $ 4.0 $ 2.6 $ 8.0