RESTATEMENT OF CONSOLIDATED FINANCIAL STATEMENTS - Restated Consolidated Statements of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												6 Months Ended		9 Months Ended		12 Months Ended			36 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2018	Mar. 31, 2017	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2019
Revenue	$ 38,225	$ 37,646	$ 34,406	$ 33,522	$ 42,125	$ 33,592	$ 31,532	$ 25,259	$ 31,779	$ 26,301	$ 21,787	$ 21,569	$ 56,791	$ 43,356	$ 90,383	$ 69,657	$ 143,799	$ 132,508	$ 101,436
Costs of sales						23,747	22,360	19,078	25,802	19,959	15,342	15,272	41,438	30,614	65,185	50,573	105,680	96,832	76,375
Gross profit	8,987	9,779	9,243	10,110	10,478	9,845	9,172	6,181	5,977	6,342	6,445	6,297	15,353	12,742	25,198	19,084	38,119	35,676	25,061
Operating expenses:
Selling, general and administrative						9,629	9,005	6,924	8,134	6,542	6,029	7,472	15,929	13,501	25,558	20,043	47,068	34,647	28,177
Depreciation and amortization						1,105	737	245	244	259	307	208	982	515	2,087	774	4,430	3,204	1,018
Total operating expenses						12,411	13,077	7,931	8,378	6,801	6,336	7,680	21,008	14,016	33,419	20,817	68,275	44,899	29,195
Operating loss	(10,143)	(3,892)	(10,200)	(5,921)	(1,002)	(2,566)	(3,905)	(1,750)	(2,401)	(459)	109	(1,383)	(5,655)	(1,274)	(8,221)	(1,733)	(30,156)	(9,223)	(4,134)
Other income (expense):
Interest income						226	324	80	95	114	200	73	404	273	630	387	1,382	943	482
Interest expense						(863)	(770)	(473)	(606)	(557)	(518)	(547)	(1,243)	(1,065)	(2,106)	(1,622)	(2,992)	(3,105)	(2,228)
Change in fair value of warrant liabilities										0	0	(1,490)		(1,490)		(1,490)	0	0	(1,490)
Total other expense, net						(637)	(446)	(393)	(511)	(443)	(318)	(1,964)	(839)	(2,282)	(1,476)	(2,725)	(1,610)	(2,162)	(3,236)
Loss before income taxes						(3,203)	(4,351)	(2,143)	(2,912)	(902)	(209)	(3,347)	(6,494)	(3,556)	(9,697)	(4,458)	(31,766)	(11,385)	(7,370)
Provision for income taxes						(20)	157	(28)	(26)	(23)	(23)	(23)	129	(46)	109	(69)	(262)	101	(95)
Net loss	(10,541)	(4,510)	(10,657)	(6,320)	(1,696)	(3,223)	(4,194)	(2,171)	(2,938)	(925)	(232)	(3,370)	(6,365)	(3,602)	(9,588)	(4,527)	(32,028)	(11,284)	(7,465)	$ (50,800)
Preferred dividends	0	(334)	0	(334)	0	(334)	0	(334)	0	(334)	0	(334)	(334)	(334)	(668)	(668)	(668)	(668)	(668)
Net loss applicable to common shares	$ (10,541)	$ (4,844)	$ (10,657)	$ (6,654)	$ (1,696)	$ (3,557)	$ (4,194)	$ (2,505)	$ (2,938)	$ (1,259)	$ (232)	$ (3,704)	$ (6,699)	$ (3,936)	$ (10,256)	$ (5,195)	$ (32,696)	$ (11,952)	$ (8,133)
Net loss per common share
Basic (in USD per share)	$ (0.18)	$ (0.08)	$ (0.18)	$ (0.11)	$ (0.03)	$ (0.07)	$ (0.08)	$ (0.05)	$ (0.07)	$ (0.03)	$ (0.01)	$ (0.10)	$ (0.13)	$ (0.10)	$ (0.20)	$ (0.13)	$ (0.54)	$ (0.23)	$ (0.20)
Diluted (in USD per share)	$ (0.18)	$ (0.08)	$ (0.18)	$ (0.11)	$ (0.03)	$ (0.07)	$ (0.08)	$ (0.05)	$ (0.07)	$ (0.03)	$ (0.01)	$ (0.10)	$ (0.13)	$ (0.10)	$ (0.20)	$ (0.13)	$ (0.54)	$ (0.23)	$ (0.20)
Weighted average number of common shares outstanding
Basic (in shares)	60,065,978	60,065,053	60,059,936	60,053,912	54,064,750	53,637,085	52,150,106	47,573,364	40,331,993	40,327,697	40,308,934	38,488,005	49,861,735	39,398,469	51,101,813	39,703,690	60,061,243	51,840,518	39,860,335
Diluted (in shares)	60,065,978	60,065,053	60,059,936	60,053,912	54,064,750	53,637,085	52,150,106	47,573,364	40,331,993	40,327,697	40,308,934	38,488,005	49,861,735	39,398,469	51,101,813	39,703,690	60,061,243	51,840,518	39,860,335
Service
Revenue						$ 25,381	$ 23,514	$ 19,397	$ 18,676	$ 17,458	$ 16,637	$ 16,363	$ 42,911	$ 33,000	$ 68,292	$ 50,458	$ 123,554	$ 96,872	$ 69,134
Costs of sales						16,037	14,356	13,247	12,442	11,733	11,246	11,099	27,603	22,345	43,640	34,078	80,485	61,175	46,520
Product
Revenue						8,211	8,018	5,862	13,103	8,843	5,150	5,206	13,880	10,356	22,091	19,199	20,245	35,636	32,302
Costs of sales						7,710	8,004	5,831	13,360	8,226	4,096	4,173	13,835	8,269	21,545	16,495	$ 25,195	$ 35,657	29,855
As Previously Reported
Revenue						35,832	32,506	25,617	34,289	26,460	21,756	21,588	58,123	43,344	93,955	69,804			104,093
Costs of sales						23,888	23,305	18,416	26,769	19,835	15,422	15,421	41,721	30,843	65,609	50,678			77,447
Gross profit						11,944	9,201	7,201	7,520	6,625	6,334	6,167	16,402	12,501	28,346	19,126			26,646
Operating expenses:
Selling, general and administrative						9,572	8,329	6,746	6,844	5,947	5,793	6,909	15,075	12,702	24,647	18,649			25,493
Depreciation and amortization						1,125	737	245	244	259	307	208	982	515	2,107	774			1,018
Total operating expenses						12,444	12,401	7,753	7,088	6,206	6,100	7,117	20,154	13,217	32,598	19,423			26,511
Operating loss						(500)	(3,200)	(552)	432	419	234	(950)	(3,752)	(716)	(4,252)	(297)			135
Other income (expense):
Interest income						134	251	80	95	114	200	73	331	273	465	387			482
Interest expense						(612)	(494)	(209)	(291)	(188)	(201)	(212)	(703)	(413)	(1,315)	(601)			(892)
Change in fair value of warrant liabilities										0	0	(1,490)		(1,490)		(1,490)			(1,490)
Total other expense, net						(478)	(243)	(129)	(196)	(74)	(1)	(1,629)	(372)	(1,630)	(850)	(1,704)			(1,900)
Loss before income taxes						(978)	(3,443)	(681)	236	345	233	(2,579)	(4,124)	(2,346)	(5,102)	(2,001)			(1,765)
Provision for income taxes						2,138	(9,073)	468	7	(209)	0	115	(8,605)	115	(6,467)	(94)			(87)
Net loss						1,160	(12,516)	(213)	243	136	233	(2,464)	(12,729)	(2,231)	(11,569)	(2,095)			(1,852)
Preferred dividends						(334)	0	(334)	0	(334)	0	(334)	(334)	(334)	(668)	(668)			(668)
Net loss applicable to common shares						$ 826	$ (12,516)	$ (547)	$ 243	$ (198)	$ 233	$ (2,798)	$ (13,063)	$ (2,565)	$ (12,237)	$ (2,763)			$ (2,520)
Net loss per common share
Basic (in USD per share)						$ 0.02	$ (0.24)	$ (0.01)	$ 0.01	$ 0.00	$ 0.01	$ (0.07)	$ (0.26)	$ (0.07)	$ (0.24)	$ (0.07)			$ (0.06)
Diluted (in USD per share)						$ 0.02	$ (0.24)	$ (0.01)	$ 0.01	$ 0.00	$ 0.01	$ (0.07)	$ (0.26)	$ (0.07)	$ (0.24)	$ (0.07)			$ (0.06)
Weighted average number of common shares outstanding
Basic (in shares)						53,637,085	52,150,106	47,573,364	40,331,993	40,327,697	40,308,934	38,488,005	49,861,735	39,398,469	51,101,813	39,703,690			39,860,335
Diluted (in shares)						54,234,566	52,150,106	47,573,364	40,772,482	40,327,697	40,730,712	38,488,005	49,861,735	39,398,469	51,101,813	39,703,690			39,860,335
As Previously Reported | Service
Revenue						$ 27,020	$ 22,853	$ 19,944	$ 18,679	$ 17,459	$ 16,639	$ 16,365	$ 42,797	$ 33,004	$ 69,817	$ 50,463			$ 69,142
Costs of sales						16,012	14,362	13,326	12,545	11,876	11,389	11,243	27,688	22,632	43,700	34,508			47,053
As Previously Reported | Product
Revenue						8,812	9,653	5,673	15,610	9,001	5,117	5,223	15,326	10,340	24,138	19,341			34,951
Costs of sales						7,876	8,943	5,090	14,224	7,959	4,033	4,178	14,033	8,211	21,909	16,170			30,394
Adjustments
Revenue						(2,240)	(974)	(358)	(2,510)	(159)	31	(19)	(1,332)	12	(3,572)	(147)			(2,657)
Costs of sales						(141)	(945)	662	(967)	124	(80)	(149)	(283)	(229)	(424)	(105)			(1,072)
Gross profit						(2,099)	(29)	(1,020)	(1,543)	(283)	111	130	(1,049)	241	(3,148)	(42)			(1,585)
Operating expenses:
Selling, general and administrative						57	676	178	1,290	595	236	563	854	799	911	1,394			2,684
Depreciation and amortization						(20)	0	0	0	0	0	0	0	0	(20)	0			0
Total operating expenses						(33)	676	178	1,290	595	236	563	854	799	821	1,394			2,684
Operating loss						(2,066)	(705)	(1,198)	(2,833)	(878)	(125)	(433)	(1,903)	(558)	(3,969)	(1,436)			(4,269)
Other income (expense):
Interest income						92	73	0	0	0	0	0	73	0	165	0			0
Interest expense						(251)	(276)	(264)	(315)	(369)	(317)	(335)	(540)	(652)	(791)	(1,021)			(1,336)
Change in fair value of warrant liabilities										0	0	0		0		0			0
Total other expense, net						(159)	(203)	(264)	(315)	(369)	(317)	(335)	(467)	(652)	(626)	(1,021)			(1,336)
Loss before income taxes						(2,225)	(908)	(1,462)	(3,148)	(1,247)	(442)	(768)	(2,370)	(1,210)	(4,595)	(2,457)			(5,605)
Provision for income taxes						(2,158)	9,230	(496)	(33)	186	(23)	(138)	8,734	(161)	6,576	25			(8)
Net loss						(4,383)	8,322	(1,958)	(3,181)	(1,061)	(465)	(906)	6,364	(1,371)	1,981	(2,432)			(5,613)
Preferred dividends						0	0	0	0	0	0	0	0	0	0	0			0
Net loss applicable to common shares						$ (4,383)	$ 8,322	$ (1,958)	$ (3,181)	$ (1,061)	$ (465)	$ (906)	$ 6,364	$ (1,371)	$ 1,981	$ (2,432)			$ (5,613)
Net loss per common share
Basic (in USD per share)						$ (0.09)	$ 0.16	$ (0.04)	$ (0.08)	$ (0.03)	$ (0.02)	$ (0.03)	$ 0.13	$ (0.03)	$ 0.04	$ (0.06)			$ (0.14)
Diluted (in USD per share)						$ (0.09)	$ 0.16	$ (0.04)	$ (0.08)	$ (0.03)	$ (0.02)	$ (0.03)	$ 0.13	$ (0.03)	$ 0.04	$ (0.06)			$ (0.14)
Weighted average number of common shares outstanding
Basic (in shares)						0	0	0	0	0	0	0	0	0	0	0			0
Diluted (in shares)						(597,481)	0	0	(440,489)	0	(421,778)	0	0	0	0	0			0
Adjustments | Service
Revenue						$ (1,639)	$ 661	$ (547)	$ (3)	$ (1)	$ (2)	$ (2)	$ 114	$ (4)	$ (1,525)	$ (5)			$ (8)
Costs of sales						25	(6)	(79)	(103)	(143)	(143)	(144)	(85)	(287)	(60)	(430)			(533)
Adjustments | Product
Revenue						(601)	(1,635)	189	(2,507)	(158)	33	(17)	(1,446)	16	(2,047)	(142)			(2,649)
Costs of sales						$ (166)	$ (939)	$ 741	$ (864)	$ 267	$ 63	$ (5)	$ (198)	$ 58	$ (364)	$ 325			$ (539)