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

Schedule I - Condensed Financial Information of Registrant - Notes to Condensed Financial Statements (Details)

v3.21.2
Schedule I - Condensed Financial Information of Registrant - Notes to Condensed Financial Statements (Details)
$ in Thousands
3 Months Ended 9 Months Ended 12 Months Ended
Mar. 29, 2021
Sep. 30, 2021
USD ($)
Sep. 30, 2020
USD ($)
Sep. 30, 2021
USD ($)
Sep. 30, 2020
USD ($)
Dec. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Aug. 18, 2017
Stock split, conversion ratio 0.333                
Income tax expense (benefit)   $ 3,270 $ (1,376) $ 8,361 $ 1,975 $ (3,144) $ 12,053 $ (1,197)  
DoubleVerify Inc.                  
Ownership percentage acquired                 100.00%
Parent Company | Reportable Legal Entities                  
Stock split, conversion ratio 0.333                
Income tax expense (benefit)           (3,144) 12,053 (1,197)  
Distributions from subsidiaries           $ 0 $ 0 $ 0  
Parent Company | Reportable Legal Entities | DoubleVerify Inc.                  
Ownership percentage acquired                 100.00%