v3.26.1
Current Expected Credit Losses (CECL) - Current Expected Credit Losses (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Financing Receivable, Allowance for Credit Loss [Roll Forward]        
Beginning balance $ 24.1 $ 28.3 $ 24.2 $ 27.2
Current-period provision for expected credit losses 1.1 0.9 1.0 2.0
Release of allowance for expected credit losses   (4.0)   (4.0)
Ending balance 25.2 25.2 25.2 25.2
Accrued commissions and other receivables, net        
Financing Receivable, Allowance for Credit Loss [Roll Forward]        
Beginning balance 6.3 6.2 6.2 6.2
Current-period provision for expected credit losses 0.8 0.9 0.9 0.9
Release of allowance for expected credit losses   0.0   0.0
Ending balance 7.1 7.1 7.1 7.1
Receivables from broker-dealers, clearing organizations, customers and related broker-dealers        
Financing Receivable, Allowance for Credit Loss [Roll Forward]        
Beginning balance 17.8 22.1 18.0 21.0
Current-period provision for expected credit losses 0.3 0.0 0.1 1.1
Release of allowance for expected credit losses   (4.0)   (4.0)
Ending balance $ 18.1 $ 18.1 $ 18.1 $ 18.1