Significant Accounting Policies - Summary of Revenue Recognized from Contract Liabilities and Remaining Balance (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	$ 4,248
Payments received in advance of services to be performed	7,024
Revenue recognized for services performed during the period	(6,457)
Foreign Currency Translation	10
Deferred revenues, ending balance	4,825
Information Services [Member]
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	3,203
Payments received in advance of services to be performed	2,417
Revenue recognized for services performed during the period	(2,454)
Deferred revenues, ending balance	3,166
Post-trade Services [Member]
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	1,045
Payments received in advance of services to be performed	4,607
Revenue recognized for services performed during the period	(4,003)
Foreign Currency Translation	10
Deferred revenues, ending balance	$ 1,659