General form of registration statement for all companies including face-amount certificate companies

Description of Business (Details)

v3.21.2
Description of Business (Details) - segment
9 Months Ended 12 Months Ended
Sep. 30, 2021
Dec. 31, 2020
Aug. 18, 2017
Description of Business      
Number of reportable segments 1 1  
DoubleVerify Inc.      
Description of Business      
Ownership percentage acquired     100.00%