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Related Party Transactions (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Jan. 01, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Related Party Transaction [Line Items]
Sublease rental income		$ 2,940	$ 2,376	$ 8,637	$ 6,565
Stagwell Subsidiary [Member] \| Services Provided By Subisidiary [Member]
Related Party Transaction [Line Items]
Due to Related Parties		816		816
Accounts Payable, Related Parties		225		225
Stagwell Subsidiary [Member] \| Development of Advertising Technology [Member]
Related Party Transaction [Line Items]
Due to Related Parties		475		475
Accounts Payable, Related Parties		17		17
Stagwell Affiliate [Member] \| Affiliated Entity [Member] \| Arrangement To Perform Media, Planning, Buying And Reporting Services [Member]
Related Party Transaction [Line Items]
Accounts receivable, related parties, current		5,276		5,276
Due from (to) from related parties		957		957
Stagwell Affiliate [Member] \| Affiliated Entity [Member] \| Arrangement To Provide Audience And Brand Research, Concept Testing And Landscape For New Business [Member]
Related Party Transaction [Line Items]
Due from (to) from related parties		(82)		(82)
Accounts payable, related parties, current		$ 145		$ 145
Other Company [Member] \| Board of Directors Chairman [Member]
Related Party Transaction [Line Items]
Sublease rental income	$ 140