v3.26.1
Current Expected Credit Losses (CECL) - Narrative (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Dec. 31, 2024
Financing Receivable, Allowance for Credit Loss [Line Items]        
Current-period provision for expected credit losses $ (0.1) $ 1.1    
Current expected credit losses reserve 24.1 28.3 $ 24.2 $ 27.2
Accrued commissions and other receivables, net        
Financing Receivable, Allowance for Credit Loss [Line Items]        
Current-period provision for expected credit losses 0.1 0.0    
Current expected credit losses reserve 6.3 6.2 6.2 6.2
Receivables from broker-dealers, clearing organizations, customers and related broker-dealers        
Financing Receivable, Allowance for Credit Loss [Line Items]        
Current-period provision for expected credit losses (0.2) 1.1    
Current expected credit losses reserve $ 17.8 $ 22.1 $ 18.0 $ 21.0