Significant Accounting Policies - Summary of Revenue Recognized from Contract Liabilities and Remaining Balance (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	$ 3,499
Payments received in advance of services to be performed	25,089
Revenue recognized for services performed during the period	(24,390)
Foreign Currency Translation	50
Deferred revenues, ending balance	4,248
Information Services [Member]
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	2,138
Payments received in advance of services to be performed	9,593
Revenue recognized for services performed during the period	(8,528)
Deferred revenues, ending balance	3,203
Post-trade Services [Member]
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	1,361
Payments received in advance of services to be performed	15,496
Revenue recognized for services performed during the period	(15,862)
Foreign Currency Translation	50
Deferred revenues, ending balance	$ 1,045