Significant Accounting Policies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) Revenue	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Significant Accounting Policies [Line Items]
Maximum maturity period for classification of investments as cash equivalents	3 months
Allowance for credit losses	$ 140	$ 163
Provision for bad debts	200	500	$ 300
Write-offs and other charges against the allowance for credit losses	$ 100	$ 100
Number of revenue streams | Revenue	4
Description of commission revenue	For Open Trading trades that the Company executes between and among institutional investor and broker-dealer clients on a matched principal basis by serving as counterparty to both the buyer and the seller, the Company earns its commission through the difference in price between the two trades.
Settlement days of bond transaction	within one to two trading days
Maximum [Member]
Significant Accounting Policies [Line Items]
Contractual maturities accounts receivable	1 year
Estimated useful life of fixed assets	7 years
Hosting service contract, amortization period	5 years
Maximum [Member] | Business Combinations [Member]
Significant Accounting Policies [Line Items]
Estimated life of intangible assets	15 years
Minimum [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of fixed assets	3 years
Hosting service contract, amortization period	1 year
Minimum [Member] | Business Combinations [Member]
Significant Accounting Policies [Line Items]
Estimated life of intangible assets	1 year
Minimum [Member] | Internally Developed Software [Member]
Significant Accounting Policies [Line Items]
Estimated life of intangible assets	3 years
ASU 2018-15 [Member]
Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Retrospective Application Impracticable [true false]	false
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
ASU 2017-04 [Member]
Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Retrospective Application Impracticable [true false]	false
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
ASU 2016-13 [Member]
Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Retrospective Application Impracticable [true false]	false
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true