Selected Quarterly Information (Unaudited) - 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
Revenue from External Customer [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
Calculated under Revenue Guidance in Effect before Topic 606
Revenue from External Customer [Line Items]
Total revenue	70,470	69,387	66,911	59,579					266,347
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue from External Customer [Line Items]
Total revenue	(1,852)	(3,232)	(1,636)	725					(5,995)
SaaS subscriptions
Revenue from External Customer [Line Items]
Total revenue	26,381	24,573	22,796	21,278					95,028
SaaS subscriptions | Calculated under Revenue Guidance in Effect before Topic 606
Revenue from External Customer [Line Items]
Total revenue	25,822	23,659	22,014	20,611
SaaS subscriptions | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue from External Customer [Line Items]
Total revenue	559	914	782	667
Term license subscriptions
Revenue from External Customer [Line Items]
Total revenue	11,569	9,199	10,103	9,557					40,428
Term license subscriptions | Calculated under Revenue Guidance in Effect before Topic 606
Revenue from External Customer [Line Items]
Total revenue	17,256	16,776	16,011	12,974
Term license subscriptions | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue from External Customer [Line Items]
Total revenue	(5,687)	(7,577)	(5,908)	(3,417)
Maintenance and support
Revenue from External Customer [Line Items]
Total revenue	4,158	4,002	3,961	3,722					15,843
Maintenance and support | Calculated under Revenue Guidance in Effect before Topic 606
Revenue from External Customer [Line Items]
Total revenue	1,240	1,164	1,234	1,324
Maintenance and support | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue from External Customer [Line Items]
Total revenue	2,918	2,838	2,727	2,398
Professional services
Revenue from External Customer [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
Professional services | Calculated under Revenue Guidance in Effect before Topic 606
Revenue from External Customer [Line Items]
Total revenue	26,152	27,788	27,652	24,670					106,262
Professional services | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue from External Customer [Line Items]
Total revenue	$ 358	$ 593	$ 763	$ 1,077					$ 2,791