Significant Accounting Policies - Revenue by Services (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 68,618	$ 66,155	$ 65,275	$ 60,304	$ 60,216	$ 54,948	$ 59,883	$ 51,696	$ 260,352	$ 226,743	$ 176,737
SaaS subscriptions
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	26,381	24,573	22,796	21,278					95,028
Term license subscriptions
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	11,569	9,199	10,103	9,557					40,428
Maintenance and support
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	4,158	4,002	3,961	3,722					15,843
Professional services
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 26,510	$ 28,381	$ 28,415	$ 25,747	$ 25,108	$ 24,043	$ 26,836	$ 24,744	$ 109,053	$ 100,731	$ 85,223