Segment and Geographic Information - Summary (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) Segment	Mar. 31, 2018 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | Segment	1
Segment Reporting Information [Line Items]
Revenues	$ 347,077	$ 326,788
United States
Segment Reporting Information [Line Items]
Revenues	189,372	171,944
International
Segment Reporting Information [Line Items]
Revenues	157,705	154,844
Europe
Segment Reporting Information [Line Items]
Revenues	135,276	130,614
Other geographies
Segment Reporting Information [Line Items]
Revenues	$ 22,429	$ 24,230