Fair Value Measurements - Summary of Categorization of Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Assets:
Securities owned, at fair value	$ 125,110	$ 127,166
Liabilities:
Deferred consideration (Note 9)	164,757	228,062
Fair Value, Measurements, Recurring [Member]
Assets:
Cash equivalents	284	11,488
Total	137,433	138,654
Liabilities:
Deferred consideration (Note 9)	164,757	228,062
Fair Value, Measurements, Recurring [Member] \| Securrency Convertible Note [Member]
Investments in Convertible Notes
Investments, Fair value disclosure	5,844
Fair Value, Measurements, Recurring [Member] \| ETFs [Member]
Assets:
Securities owned, at fair value	12,621	18,812
Fair Value, Measurements, Recurring [Member] \| Pass-through GSEs [Member]
Assets:
Securities owned, at fair value	102,248	106,245
Fair Value, Measurements, Recurring [Member] \| Corporate Bonds [Member]
Assets:
Securities owned, at fair value	1,804	2,109
Fair Value, Measurements, Recurring [Member] \| U.S. treasuries
Assets:
Securities owned, at fair value	8,437
Fair Value, Measurements, Nonrecurring [Member] \| Onramp Preferred Stock [Member]
Assets:
Investment owned, at fair value	312
Securrency - Series A convertible preferred stock \| Fair Value, Measurements, Nonrecurring [Member]
Assets:
Investment owned, at fair value		8,488
Fnality Convertible Note [Member] \| Fair Value, Measurements, Recurring [Member]
Investments in Convertible Notes
Investments, Fair value disclosure	6,195
Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets:
Cash equivalents	284	11,488
Total	45,036	55,020
Liabilities:
Deferred consideration (Note 9)	0	0
Level 1 [Member] \| Fair Value, Measurements, Recurring [Member] \| Securrency Convertible Note [Member]
Investments in Convertible Notes
Investments, Fair value disclosure	0
Level 1 [Member] \| Fair Value, Measurements, Recurring [Member] \| ETFs [Member]
Assets:
Securities owned, at fair value	12,621	18,812
Level 1 [Member] \| Fair Value, Measurements, Recurring [Member] \| Pass-through GSEs [Member]
Assets:
Securities owned, at fair value	23,694	24,720
Level 1 [Member] \| Fair Value, Measurements, Recurring [Member] \| Corporate Bonds [Member]
Assets:
Securities owned, at fair value	0	0
Level 1 [Member] \| Fair Value, Measurements, Recurring [Member] \| U.S. treasuries
Assets:
Securities owned, at fair value	8,437
Level 1 [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Onramp Preferred Stock [Member]
Assets:
Investment owned, at fair value	0
Level 1 [Member] \| Securrency - Series A convertible preferred stock \| Fair Value, Measurements, Nonrecurring [Member]
Assets:
Investment owned, at fair value		0
Level 1 [Member] \| Fnality Convertible Note [Member] \| Fair Value, Measurements, Recurring [Member]
Investments in Convertible Notes
Investments, Fair value disclosure	0
Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets:
Cash equivalents	0	0
Total	80,358	83,634
Liabilities:
Deferred consideration (Note 9)	0	0
Level 2 [Member] \| Fair Value, Measurements, Recurring [Member] \| Securrency Convertible Note [Member]
Investments in Convertible Notes
Investments, Fair value disclosure	0
Level 2 [Member] \| Fair Value, Measurements, Recurring [Member] \| ETFs [Member]
Assets:
Securities owned, at fair value	0	0
Level 2 [Member] \| Fair Value, Measurements, Recurring [Member] \| Pass-through GSEs [Member]
Assets:
Securities owned, at fair value	78,554	81,525
Level 2 [Member] \| Fair Value, Measurements, Recurring [Member] \| Corporate Bonds [Member]
Assets:
Securities owned, at fair value	1,804	2,109
Level 2 [Member] \| Fair Value, Measurements, Recurring [Member] \| U.S. treasuries
Assets:
Securities owned, at fair value	0
Level 2 [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Onramp Preferred Stock [Member]
Assets:
Investment owned, at fair value	0
Level 2 [Member] \| Securrency - Series A convertible preferred stock \| Fair Value, Measurements, Nonrecurring [Member]
Assets:
Investment owned, at fair value		0
Level 2 [Member] \| Fnality Convertible Note [Member] \| Fair Value, Measurements, Recurring [Member]
Investments in Convertible Notes
Investments, Fair value disclosure	0
Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets:
Cash equivalents	0	0
Total	12,039	0
Liabilities:
Deferred consideration (Note 9)	164,757	228,062
Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Securrency Convertible Note [Member]
Investments in Convertible Notes
Investments, Fair value disclosure	5,844
Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| ETFs [Member]
Assets:
Securities owned, at fair value	0	0
Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Pass-through GSEs [Member]
Assets:
Securities owned, at fair value	0	0
Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Corporate Bonds [Member]
Assets:
Securities owned, at fair value	0	0
Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| U.S. treasuries
Assets:
Securities owned, at fair value	0
Level 3 [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Onramp Preferred Stock [Member]
Assets:
Investment owned, at fair value	312
Level 3 [Member] \| Securrency - Series A convertible preferred stock \| Fair Value, Measurements, Nonrecurring [Member]
Assets:
Investment owned, at fair value		$ 8,488
Level 3 [Member] \| Fnality Convertible Note [Member] \| Fair Value, Measurements, Recurring [Member]
Investments in Convertible Notes
Investments, Fair value disclosure	$ 6,195

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Value of the investment at close of period. For schedules of investments that are categorized, the value would be aggregated by category. For investment in and advances to affiliates, if operations of any controlled companies are different in character from those of the company, group such affiliates within divisions and by type of activities.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Fair value of financial instruments held by a broker-dealer for their own account (proprietary securities) for trading or investment purposes determined by management based upon quoted prices of a financial instrument with similar characteristics or on a valuation technique or model.

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Amount of liability arising from deferred consideration in a business combination.

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