Significant Accounting Policies - Summary of Revenue Recognized from Contract Liabilities and Remaining Balance (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	$ 2,810
Payments received in advance of services to be performed	21,056
Revenue recognized for services performed during the period	(20,396)
Foreign Currency Translation	29
Deferred revenues, ending balance	3,499
Information Services [Member]
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	1,959
Payments received in advance of services to be performed	7,439
Revenue recognized for services performed during the period	(7,260)
Deferred revenues, ending balance	2,138
Post-trade Services [Member]
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	851
Payments received in advance of services to be performed	13,617
Revenue recognized for services performed during the period	(13,136)
Foreign Currency Translation	29
Deferred revenues, ending balance	$ 1,361