Goodwill - Additional Information (Details) $ in Thousands, € in Millions						12 Months Ended
	Feb. 17, 2015 USD ($)	Apr. 07, 2014 EUR (€)	Apr. 07, 2014 USD ($)	Feb. 19, 2014 EUR (€)	Feb. 19, 2014 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 EUR (€)	Dec. 31, 2013 USD ($)	Apr. 07, 2014 USD ($)	Feb. 19, 2014 USD ($)
Goodwill [Line Items]
Payments to acquire businesses, net of cash acquired						$ 235,541	$ 20,542	$ 26,103
Goodwill						209,418	41,973	27,856
Acquisition costs						$ 85	$ 324	$ 950
DataPop, Inc.
Goodwill [Line Items]
Consideration transferred	$ 22,000
Cash acquired from acquisition	3,700
Payments to acquire businesses, net of cash acquired	18,300
Goodwill	16,700
Acquisition costs	600
DataPop, Inc. | Technology Asset
Goodwill [Line Items]
Finite-lived asset acquired	$ 7,800
AdQuantic
Goodwill [Line Items]
Payments to acquire businesses, net of cash acquired		€ 3.0	$ 4,100
Goodwill		2.8									$ 3,900
Acquisition costs		€ 0.1	$ 100
Tedemis
Goodwill [Line Items]
Consideration transferred				€ 21.0	$ 29,000
Payments to acquire businesses, gross				17.0	23,400
Deferred tax assets				2.3								$ 3,200
Goodwill				15.6								21,600
Acquisition costs				0.4	500				€ 0.1	$ 100
Contingent consideration				€ 4.0	$ 5,500
Milestone period (in years)				2 years	2 years
Tedemis | Technology Asset
Goodwill [Line Items]
Finite-lived asset acquired				€ 2.8								3,900
Tedemis | Cookie Pool
Goodwill [Line Items]
Finite-lived asset acquired				€ 4.6								$ 6,300