Intangible Assets - Summary of Intangible Assets and Related Accumulated Amortization (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross value	$ 82,671	$ 68,251
Accumulated amortization	53,739	39,660
Net value	28,932	28,591
Publisher and data supply relationships
Finite-Lived Intangible Assets [Line Items]
Gross value	7,500
Accumulated amortization	1,146
Net value	6,354
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross value	2,720	2,720
Accumulated amortization	2,040	1,634
Net value	680	1,086
Completed technologies
Finite-Lived Intangible Assets [Line Items]
Gross value	20,292	20,292
Accumulated amortization	16,352	13,037
Net value	3,940	7,255
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross value	52,159	45,239
Accumulated amortization	34,201	24,989
Net value	$ 17,958	$ 20,250