Business Combination - Additional Information (Details) - Boston-based Dataxu, Inc, Demand-Side Platform (DSP) - USD ($) shares in Thousands, $ in Millions		12 Months Ended
Nov. 08, 2019	Dec. 31, 2020
Business Acquisition [Line Items]
Business combination, date of merger agreement	Oct. 22, 2019
Purchase consideration	$ 147.3
Business combination, aggregate cash consideration	77.6
Business combination, aggregate fair value	69.7
Escrow deposit related to acquisition	$ 18.8
Escrow deposit unreleased related to acquisition		$ 13.6
Class A Common Stock
Business Acquisition [Line Items]
Shares of common stock issued	571,459

Escrow deposit related to acquisition.

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Escrow deposit unreleased related to acquisition.

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Date when the business acquisition agreement was executed, in CCYY-MM-DD format.

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Number of shares of equity interests issued or issuable to acquire entity.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.

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The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

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