Significant Accounting Policies - Summary of Information Services Revenue by Timing of Recognition (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Significant Accounting Policies [Line Items]
Revenues	$ 131,597	$ 101,443	$ 381,578	$ 323,121
Information Services [Member]
Significant Accounting Policies [Line Items]
Revenues	7,693	7,174	22,215	21,170
Information Services [Member] | Transferred over Time [Member]
Significant Accounting Policies [Line Items]
Revenues	7,203	7,029	21,472	20,652
Information Services [Member] | Transferred at a Point in Time [Member]
Significant Accounting Policies [Line Items]
Revenues	$ 490	$ 145	$ 743	$ 518