Acquisition Related Liabilities - Schedule of Acquisition Related Liabilities (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Oct. 14, 2021
Schedule of acquisition related liabilities [Line Items]
Balance as of January 1, 2021	$ 23,155
Additions	1,808
Payments made during the year	(64)
Change in fair value of earn-out	(13)
Balance as of September 30, 2021	24,886
eBay CRM [Member]
Schedule of acquisition related liabilities [Line Items]
Balance as of January 1, 2021	17,137
Additions		$ 649
Change in fair value of earn-out	649
Balance as of September 30, 2021	17,786
Sizmek [Member]
Schedule of acquisition related liabilities [Line Items]
Balance as of January 1, 2021	4,402
Change in fair value of earn-out	(470)
Balance as of September 30, 2021	3,932
PlaceIQ [Member]
Schedule of acquisition related liabilities [Line Items]
Balance as of January 1, 2021	256
Payments made during the year	(64)
Change in fair value of earn-out	(192)
IgnitionOne [Member]
Schedule of acquisition related liabilities [Line Items]
Balance as of January 1, 2021	1,360
Balance as of September 30, 2021	1,360
Kinetic Data Solutions, LLC [Member]
Schedule of acquisition related liabilities [Line Items]
Additions	24
Balance as of September 30, 2021	24
Vital Digital, Corp [Member]
Schedule of acquisition related liabilities [Line Items]
Additions	1,784
Balance as of September 30, 2021	$ 1,784