Description of Business and Summary of Significant Accounting Policies - Revenue by Geographic Region (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenue	$ 249,838	$ 218,876	$ 222,779
United States
Disaggregation of Revenue [Line Items]
Revenue	146,702	137,433	146,733
Other Americas
Disaggregation of Revenue [Line Items]
Revenue	7,315	6,987	6,818
Total Americas
Disaggregation of Revenue [Line Items]
Revenue	154,017	144,420	153,551
EMEA
Disaggregation of Revenue [Line Items]
Revenue	71,318	56,310	50,511
APAC
Disaggregation of Revenue [Line Items]
Revenue	24,503	18,146	18,717
United Kingdom
Disaggregation of Revenue [Line Items]
Revenue	46,500	38,900	35,300
Netherlands
Disaggregation of Revenue [Line Items]
Revenue	$ 8,700	$ 2,000	$ 2,100