Segment Information - Reconciliation of U.S. GAAP (Loss) Income Before Income Taxes to Adjusted EBITDA (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting [Abstract]
Adjusted EBITDA		$ 14,832	$ 8,175	$ 61,288	$ 35,596
Stock-based compensation expense		(10,933)	(6,234)	(31,229)	(13,939)
Interest expense		(3,037)	(2,934)	(8,998)	(8,590)
Depreciation and amortization		(6,175)	(5,623)	(19,355)	(16,916)
Restructuring expense		124		(4,954)
Special adjustments, interest income and other	[1]	102	1,041	275	1,501
Loss before income taxes		$ (5,087)	$ (5,575)	$ (2,973)	$ (2,348)

[1] Included in 2020 are a) $1.0 million of proceeds from settlements related to an historical acquisition for both the three and nine months ended September 30, 2020, and b) $0.6 million of severance expense for the nine-months ended September 30, 2020.