Noncontrolling Interests - Additional Information (Details) - shares		6 Months Ended
	Feb. 12, 2021	Jun. 30, 2022
Minority Interest [Line Items]
Common stock, conversion basis		continuing members of Viant Technology LLC to exchange Class B units for shares of Class A common stock on a one-for-one basis
Class A Common Stock
Minority Interest [Line Items]
Exchange units for shares of common stock		1
Exchange (cancellation) of shares		24,870
Class B Units | Viant Technology LLC
Minority Interest [Line Items]
Exchange of noncontrolling interests, shares		24,870
Class B Common Stock
Minority Interest [Line Items]
Exchange (cancellation) of shares		(24,870)
Class B Common Stock | Viant Technology LLC
Minority Interest [Line Items]
Exchange (cancellation) of shares	48,935,559