Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 74,184	$ 55,065	$ 213,531	$ 156,571
Subscription and support
Disaggregation of Revenue [Line Items]
Revenue	70,992	51,059	202,582	144,757
Subscription and support | United States
Disaggregation of Revenue [Line Items]
Revenue	53,356	36,503	149,946	100,778
Subscription and support | United Kingdom
Disaggregation of Revenue [Line Items]
Revenue	9,518	9,334	28,864	28,082
Subscription and support | Canada
Disaggregation of Revenue [Line Items]
Revenue	3,318	2,501	11,260	6,233
Subscription and support | Other International
Disaggregation of Revenue [Line Items]
Revenue	4,800	2,721	12,512	9,664
Perpetual license
Disaggregation of Revenue [Line Items]
Revenue	411	975	1,263	2,207
Perpetual license | United States
Disaggregation of Revenue [Line Items]
Revenue	345	830	849	1,882
Perpetual license | United Kingdom
Disaggregation of Revenue [Line Items]
Revenue	0	20	16	37
Perpetual license | Canada
Disaggregation of Revenue [Line Items]
Revenue	14	37	71	94
Perpetual license | Other International
Disaggregation of Revenue [Line Items]
Revenue	52	88	327	194
Professional services
Disaggregation of Revenue [Line Items]
Revenue	2,781	3,031	9,686	9,607
Professional services | United States
Disaggregation of Revenue [Line Items]
Revenue	1,865	2,229	6,773	6,764
Professional services | United Kingdom
Disaggregation of Revenue [Line Items]
Revenue	432	525	1,621	1,709
Professional services | Canada
Disaggregation of Revenue [Line Items]
Revenue	137	114	371	406
Professional services | Other International
Disaggregation of Revenue [Line Items]
Revenue	$ 347	$ 163	$ 921	$ 728