Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 55,065	$ 37,144	$ 156,571	$ 104,705
Subscription and support
Disaggregation of Revenue [Line Items]
Revenue	51,059	33,919	144,757	94,802
Subscription and support | United States
Disaggregation of Revenue [Line Items]
Revenue	36,503	27,966	100,778	76,685
Subscription and support | United Kingdom
Disaggregation of Revenue [Line Items]
Revenue	9,334	1,277	28,082	4,039
Subscription and support | Canada
Disaggregation of Revenue [Line Items]
Revenue	2,501	1,355	6,233	4,084
Subscription and support | Other International
Disaggregation of Revenue [Line Items]
Revenue	2,721	3,321	9,664	9,994
Perpetual license
Disaggregation of Revenue [Line Items]
Revenue	975	915	2,207	3,224
Perpetual license | United States
Disaggregation of Revenue [Line Items]
Revenue	830	787	1,882	1,805
Perpetual license | United Kingdom
Disaggregation of Revenue [Line Items]
Revenue	20	4	37	94
Perpetual license | Canada
Disaggregation of Revenue [Line Items]
Revenue	37	71	94	251
Perpetual license | Other International
Disaggregation of Revenue [Line Items]
Revenue	88	53	194	1,074
Professional services
Disaggregation of Revenue [Line Items]
Revenue	3,031	2,310	9,607	6,679
Professional services | United States
Disaggregation of Revenue [Line Items]
Revenue	2,229	1,939	6,764	5,145
Professional services | United Kingdom
Disaggregation of Revenue [Line Items]
Revenue	525	87	1,709	237
Professional services | Canada
Disaggregation of Revenue [Line Items]
Revenue	114	107	406	455
Professional services | Other International
Disaggregation of Revenue [Line Items]
Revenue	$ 163	$ 177	$ 728	$ 842