Acquisitions - Additional Information (Detail) - USD ($) $ in Thousands			12 Months Ended
	Apr. 09, 2021	Nov. 30, 2020	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Contingent consideration payable			$ 600
Goodwill			154,789	$ 147,388
Muni Brokers L L C [Member]
Business Acquisition [Line Items]
Cash consideration	$ 17,100
Amortizable intangible assets	32,000
Goodwill	$ 7,400
Business combination, contingent consideration payment period	2 years
Muni Brokers L L C [Member] | Accounts Payable, Accrued Expenses and Other Liabilities [Member]
Business Acquisition [Line Items]
Cash consideration	$ 17,100
Contingent consideration payable	22,500
Business Combination, Consideration Transferred	39,600
Regulatory Services GmbH of Deutsche Borse Group [Member]
Business Acquisition [Line Items]
Cash consideration		$ 22,500
Amortizable intangible assets		$ 37,400
Business combination, contingent consideration payment period		18 months
Amount of increase in the value of contingent consideration payable			$ 5,500
Maximum [Member]
Business Acquisition [Line Items]
Business combination, contingent consideration payment period			24 months
Maximum [Member] | Muni Brokers L L C [Member]
Business Acquisition [Line Items]
Contingent consideration payable	$ 25,000
Maximum [Member] | Muni Brokers L L C [Member] | Customer Relationships and Technology [Member]
Business Acquisition [Line Items]
Useful lives	15 years
Maximum [Member] | Regulatory Services GmbH of Deutsche Borse Group [Member]
Business Acquisition [Line Items]
Contingent consideration payable		$ 24,600
Minimum [Member]
Business Acquisition [Line Items]
Business combination, contingent consideration payment period			18 months
Minimum [Member] | Muni Brokers L L C [Member] | Customer Relationships and Technology [Member]
Business Acquisition [Line Items]
Useful lives	1 year