Significant Accounting Policies - Summary of Revenue Recognized from Contract Liabilities and Remaining Balance (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($)
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	$ 4,248
Payments received in advance of services to be performed	13,455
Revenue recognized for services performed during the period	(13,023)
Foreign Currency Translation	15
Deferred revenues, ending balance	4,695
Information Services [Member]
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	3,203
Payments received in advance of services to be performed	5,060
Revenue recognized for services performed during the period	(4,967)
Deferred revenues, ending balance	3,296
Post-trade Services [Member]
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	1,045
Payments received in advance of services to be performed	8,395
Revenue recognized for services performed during the period	(8,056)
Foreign Currency Translation	15
Deferred revenues, ending balance	$ 1,399