Related Party Transactions (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Related Party Transaction [Line Items]
Sublease rental income		$ 2,892	$ 2,590	$ 5,697	$ 4,189
Stagwell Subsidiary [Member] | Services Provided By Subisidiary [Member]
Related Party Transaction [Line Items]
Due to Related Parties		723		723
Accounts Payable, Related Parties		200		200
Stagwell Subsidiary [Member] | Development of Advertising Technology [Member]
Related Party Transaction [Line Items]
Due to Related Parties		460		460
Accounts Payable, Related Parties		$ 170		$ 170
Other Company [Member] | Board of Directors Chairman [Member]
Related Party Transaction [Line Items]
Sublease rental income	$ 185