Revenue from Contracts with Customers - Disaggregation of Revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Total revenue	$ 54,515
Subscription Revenue [Member]
Disaggregation of Revenue [Line Items]
Total revenue	28,710
Term And Perpetual License [Member]
Disaggregation of Revenue [Line Items]
Total revenue	5,619
Maintenance and Support [Member]
Disaggregation of Revenue [Line Items]
Total revenue	10,753
Professional Services [Member]
Disaggregation of Revenue [Line Items]
Total revenue	8,483
Other [Member]
Disaggregation of Revenue [Line Items]
Total revenue	950
United States [Member]
Disaggregation of Revenue [Line Items]
Total revenue	44,210
All other [Member]
Disaggregation of Revenue [Line Items]
Total revenue	$ 10,305