Related Party Transactions - Receivables from and Payables to Related Broker-Dealers (Details) - Related Party - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Transactions with Freedom
Related Party Transaction [Line Items]
Receivables from related parties	$ 1,600,000	$ 1,400,000
Open Derivative Contracts with Cantor
Related Party Transaction [Line Items]
Receivables from related parties	2,800,000	3,100,000
Payables to related parties	4,700,000	5,800,000
Fails and Pending Trades with Cantor
Related Party Transaction [Line Items]
Receivables from related parties		0
Payables to related parties	$ 1,000,000	$ 0

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

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480833/946-310-45-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(5))
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(5)(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479617/946-210-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 954
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481058/954-310-45-1

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Balance Type:	debit
Period Type:	instant