Segment and Geographic Information - Summary of Revenue and Long-lived Assets (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 168,978	$ 124,491
Long-lived assets	74,926		$ 71,795
United States [Member]
Segment Reporting Information [Line Items]
Revenues	141,610	103,615
Long-lived assets	62,574		62,356
United Kingdom [Member]
Segment Reporting Information [Line Items]
Revenues	22,419	20,267
Long-lived assets	12,330		9,410
Other [Member]
Segment Reporting Information [Line Items]
Revenues	4,949	$ 609
Long-lived assets	$ 22		$ 29