Consolidated Statement of Operations - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Subscription and support	$ 24,756	$ 23,169	$ 19,407	$ 18,135	$ 17,062	$ 17,029	$ 16,220	$ 15,241	$ 85,467	$ 65,552	$ 57,193
Perpetual license	1,050	856	1,746	694	542	332	458	318	4,346	1,650	2,805
Total product revenue	25,806	24,025	21,153	18,829	17,604	17,361	16,678	15,559	89,813	67,202	59,998
Professional services	2,041	2,047	2,128	1,923	1,770	1,880	1,892	2,023	8,139	7,565	9,913
Total revenue	27,847	26,072	23,281	20,752	19,374	19,241	18,570	17,582	97,952	74,767	69,911
Cost of revenue:
Subscription and support	8,148	7,737	6,676	5,893	6,127	5,747	5,634	5,226	28,454	22,734	19,586
Professional services	1,355	1,376	1,327	1,135	1,056	1,045	1,106	1,624	5,193	4,831	7,085
Total cost of revenue	9,503	9,113	8,003	7,028	7,183	6,792	6,740	6,850	33,647	27,565	26,671
Gross profit	18,344	16,959	15,278	13,724	12,191	12,449	11,830	10,732	64,305	47,202	43,240
Operating expenses:
Sales and marketing	3,791	4,258	4,037	3,221	3,041	3,097	2,953	3,069	15,307	12,160	12,965
Research and development	4,223	4,092	4,003	3,477	3,218	3,737	4,054	3,910	15,795	14,919	15,778
Refundable Canadian tax credits	(118)	(195)	(112)	(117)	(173)	(115)	(116)	(109)	(542)	(513)	(470)
General and administrative	5,727	5,084	6,576	5,904	4,946	4,670	4,547	4,123	23,291	18,286	18,201
Depreciation and amortization	2,387	1,648	1,299	1,164	1,021	1,322	1,476	1,472	6,498	5,291	4,534
Acquisition-related expenses	4,724	4,399	2,278	3,691	728	1,047	1,380	2,428	15,092	5,583	2,455
Total operating expenses	20,734	19,286	18,081	17,340	12,781	13,758	14,294	14,893	75,441	55,726	53,463
Loss from operations	(2,390)	(2,327)	(2,803)	(3,616)	(590)	(1,309)	(2,464)	(4,161)	(11,136)	(8,524)	(10,223)
Other expense:
Interest expense, net	(2,210)	(2,277)	(1,160)	(935)	(849)	(709)	(662)	(561)	(6,582)	(2,781)	(1,858)
Other income (expense), net	549	(130)	(18)	(112)	427	(64)	(293)	(748)	289	(678)	(544)
Total other expense	(1,661)	(773)	(2,812)	(1,047)	(422)	(773)	(955)	(1,309)	(6,293)	(3,459)	(2,402)
Loss before provision for income taxes	(4,051)	(3,100)	(5,615)	(4,663)	(1,012)	(2,082)	(3,419)	(5,470)	(17,429)	(11,983)	(12,625)
Provision for income taxes	257	(406)	(196)	(951)	(961)	(308)	(158)	(103)	(1,296)	(1,530)	(1,039)
Net loss	$ (3,794)	$ (3,506)	$ (5,811)	$ (5,614)	$ (1,973)	$ (2,390)	$ (3,577)	$ (5,573)	$ (18,725)	$ (13,513)	$ (13,664)
Net loss per common share:
Net loss per common share, basic and diluted (in USD per share)	$ (0.19)	$ (0.18)	$ (0.33)	$ (0.33)	$ (0.12)	$ (0.14)	$ (0.22)	$ (0.36)	$ (1.02)	$ (0.82)	$ (0.91)
Weighted-average common shares outstanding, basic and diluted (in shares)									18,411,247	16,472,799	14,939,601