Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business.

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Related Party Transactions - Receivables from and Payables to Related Broker-Dealers (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Payables to related parties			$ 8.3
Related Party \| Transactions with Freedom
Related Party Transaction [Line Items]
Receivables from related parties	$ 1.4	$ 1.4
Related Party \| Open Derivative Contracts with Cantor
Related Party Transaction [Line Items]
Receivables from related parties	2.7	3.1
Payables to related parties	4.9	5.8
Related Party \| Fails and Pending Trades with Cantor
Related Party Transaction [Line Items]
Payables to related parties	$ 0.8	$ 0.0