Acquisitions - Summary of Purchase Price Allocation (Detail) - USD ($) $ in Thousands	Oct. 13, 2020	Jun. 11, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill			$ 58,043	$ 46,511	$ 74,292
Cisneros Interactive
Business Acquisition [Line Items]
Cash	$ 8,700
Accounts receivable	50,500
Other assets	6,200
Intangible assets subject to amortization	41,700
Goodwill	12,300
Current liabilities	(48,100)
Deferred tax	(10,600)
Redeemable noncontrolling interest	(30,800)
Purchase price consideration	$ 29,900
Smadex
Business Acquisition [Line Items]
Cash		$ 1,200
Accounts receivable		900
Other assets		400
Intangible assets subject to amortization		2,000
Goodwill		3,600
Current liabilities		(2,800)
Deferred tax		(400)
Purchase price consideration		3,500
Long-term liabilities		$ (200)