UNAUDITED QUARTERLY DATA - Effect of Restatement on Previously Filed Statement of Cash Flows (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended												6 Months Ended		9 Months Ended		12 Months Ended			36 Months Ended
	Dec. 31, 2017	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
OPERATING ACTIVITIES:
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)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Non-cash stock-based compensation									409				211	984	445	1,424	678	1,750	1,794	1,214
(Gain) loss on disposal of property and equipment									(18)					(80)	(34)	(99)	(59)	672	(131)	(177)
Non-cash interest and amortization of debt discount									17				139	94	65	118	98	301	140	113
Bad debt expense									168				199	382	331	510	460	2,534	471	557
Provision for inventory reserve									221				248	1,091	480	1,361	804	3,172	1,467	877
Depreciation and amortization									1,370				1,603	3,278	3,164	5,586	4,679	8,009	7,829	5,956
Excess tax benefits									67					67		67		0	67	0
Change in fair value of warrant liabilities											0	0	1,490		1,490		1,490	0	0	1,490
Deferred income taxes, net									16				15	(159)	30	(154)	46	(7)	(183)	62
Recognition of deferred gain from sale-leaseback transactions									0				0	0	0	0	0			0
Changes in operating assets and liabilities:
Accounts receivable									(3,149)				(1,003)	(5,332)	(2,418)	(9,964)	(2,316)	(8,488)	(6,234)	(2,538)
Finance receivables, net									9,168				(5)	7,332	2,119	8,202	(2,180)	(8)	2,228	(10,832)
Sale of finance receivables																2,051		0	2,280	0
Inventory, net									(3,900)				(2,713)	(7,615)	(3,403)	(7,777)	(2,957)	(5,242)	(3,661)	(4,463)
Prepaid expenses and other current assets									(103)				(124)	(2)	(442)	355	(454)	(395)	377	153
Accounts payable and accrued expenses									(1,490)				(2,543)	7,704	(2,700)	15,255	1,262	873	16,933	8,874
Deferred revenue									171				(59)	570	326	351	157	(98)	351	115
Income taxes payable									(55)				(3)	(40)	3	(30)	4	254	(13)	(8)
Net cash (used in) provided by operating activities									721				(5,915)	1,909	(4,146)	7,668	(2,815)	(28,701)	12,431	(6,072)
INVESTING ACTIVITIES:
Purchase of property and equipment, including rentals									(720)				(623)	(1,734)	(1,752)	(3,138)	(2,536)	(4,346)	(3,978)	(3,787)
Proceeds from sale of property and equipment									45					157	61	252	105	116	298	348
Cash paid for acquisitions, net of cash acquired														(65,181)		(65,181)		0	(65,181)	0
Net cash used in investing activities									(675)				(623)	(66,758)	(1,691)	(68,067)	(2,431)	(4,230)	(68,861)	(3,439)
FINANCING ACTIVITIES:
Proceeds from collateralized borrowing from the transfer of finance receivables	$ 1,100													1,075		1,075		0	1,075	0
Cash used in retirement of common stock													(31)		(31)	(156)	(31)	(81)	(552)	(31)
Proceeds from exercise of common stock warrants													6,193		6,193		6,193	0	0	6,193
Payment of debt issuance costs														445		445	90	156	445	90
Proceeds from exercise of common stock options																109		42	141	0
Proceeds from issuance of long-term debt														25,100		25,100		0	25,100	0
Proceeds from revolving credit facility														10,000		12,500		0	12,500	0
Repayment of revolving credit facility																(2,500)		0	(2,500)	0
Issuance of common stock in public offering, net									39,888					39,888		39,888		0	104,796	0
Repayment of line of credit														(7,111)	(106)	(7,111)	(106)	0	(7,111)	(106)
Repayment of capital lease obligations and long-term debt									(809)				(698)	(1,043)	(1,457)	(3,751)	(2,212)	(23,254)	(5,355)	(2,982)
Net cash (used in) provided by financing activities									39,079				5,464	67,464	4,599	64,709	3,754	(23,569)	127,649	2,984
Net (decrease) increase in cash and cash equivalents									39,125				(1,074)	2,615	(1,238)	4,310	(1,492)	(56,500)	71,219	(6,527)
Cash and cash equivalents at beginning of year					$ 83,964	17,055	15,360	51,870	12,745	17,780	18,034	18,198	19,272	12,745	19,272	12,745	19,272	83,964	12,745	19,272	19,272
Cash and cash equivalents at end of year	15,360	$ 27,464				83,964	17,055	15,360	51,870	12,745	17,780	18,034	18,198	15,360	18,034	17,055	17,780	$ 27,464	83,964	12,745	27,464
As Previously Reported
OPERATING ACTIVITIES:
Net loss							1,160	(12,516)	(213)	243	136	233	(2,464)	(12,729)	(2,231)	(11,569)	(2,095)			(1,852)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Non-cash stock-based compensation									576				211	1,356	445	2,005	678			1,214
(Gain) loss on disposal of property and equipment									(18)					(83)	(31)	(112)	(59)			(177)
Non-cash interest and amortization of debt discount									15				105	86	26	100	98			113
Bad debt expense									118				97	291	450	506	577			764
Provision for inventory reserve									0				0	0	0	0	0			0
Depreciation and amortization									1,492				1,301	3,476	2,564	5,858	3,774			5,591
Excess tax benefits									67					67		67
Change in fair value of warrant liabilities											0	0	1,490		1,490		1,490			1,490
Deferred income taxes, net									(535)				(115)	8,537	(115)	6,400	94			54
Recognition of deferred gain from sale-leaseback transactions									(43)				(215)	(93)	(430)	(143)	(646)			(560)
Changes in operating assets and liabilities:
Accounts receivable									(3,192)				(1,038)	(5,290)	(2,347)	(12,972)	(2,388)			(2,988)
Finance receivables, net									8,771				(5)	7,958	2,119	11,114	(2,113)			(12,119)
Sale of finance receivables																0
Inventory, net									(3,648)				(2,223)	(5,822)	(2,689)	(5,624)	(2,042)			(2,399)
Prepaid expenses and other current assets									(217)				(224)	(606)	(542)	(564)	(406)			(304)
Accounts payable and accrued expenses									(2,168)				(3,175)	6,950	(3,840)	13,808	(1,239)
Deferred revenue									0				0	0	0	(185)	0			0
Income taxes payable									0				(10)	40	(12)	0	(18)			(8)
Net cash (used in) provided by operating activities									1,005				(6,265)	4,138	(5,143)	8,689	(4,295)			(6,771)
INVESTING ACTIVITIES:
Purchase of property and equipment, including rentals									(992)				(810)	(1,767)	(1,944)	(3,005)	(2,818)			(4,041)
Proceeds from sale of property and equipment									45					157	61	252	105			348
Cash paid for acquisitions, net of cash acquired														(65,181)		(65,181)
Net cash used in investing activities									(947)				(810)	(66,791)	(1,883)	(67,934)	(2,713)			(3,693)
FINANCING ACTIVITIES:
Proceeds from collateralized borrowing from the transfer of finance receivables														0		0
Cash used in retirement of common stock													(31)		(31)	(156)	(31)			(31)
Proceeds from exercise of common stock warrants													6,193		6,193		6,193			6,193
Payment of debt issuance costs														445		445	90			90
Proceeds from exercise of common stock options																109
Proceeds from issuance of long-term debt														25,100		25,100
Proceeds from revolving credit facility														10,000		12,500
Repayment of revolving credit facility																(2,500)
Issuance of common stock in public offering, net									39,888					39,888		39,888
Repayment of line of credit														(7,111)	0	(7,111)	0			(106)
Repayment of capital lease obligations and long-term debt									(821)				(161)	(2,138)	(374)	(3,778)	(556)			(2,029)
Net cash (used in) provided by financing activities									39,067				6,001	65,294	5,788	63,607	5,516			3,937
Net (decrease) increase in cash and cash equivalents									39,125				(1,074)	2,641	(1,238)	4,362	(1,492)			(6,527)
Cash and cash equivalents at beginning of year						17,107	15,386	51,870	12,745	17,780	18,034	18,198	19,272	12,745	19,272	12,745	19,272		12,745	19,272	19,272
Cash and cash equivalents at end of year	15,386						17,107	15,386	51,870	12,745	17,780	18,034	18,198	15,386	18,034	17,107	17,780			12,745
Adjustments
OPERATING ACTIVITIES:
Net loss							(4,383)	8,322	(1,958)	(3,181)	(1,061)	(465)	(906)	6,364	(1,371)	1,981	(2,432)			(5,613)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Non-cash stock-based compensation									(167)				0	(372)	0	(581)	0			0
(Gain) loss on disposal of property and equipment									0					3	(3)	13	0			0
Non-cash interest and amortization of debt discount									2				34	8	39	18	0			0
Bad debt expense									50				102	91	(119)	4	(117)			(207)
Provision for inventory reserve									221				248	1,091	480	1,361	804			877
Depreciation and amortization									(122)				302	(198)	600	(272)	905			365
Excess tax benefits									0					0		0
Change in fair value of warrant liabilities											0	0	0		0		0			0
Deferred income taxes, net									551				130	(8,696)	145	(6,554)	(48)			8
Recognition of deferred gain from sale-leaseback transactions									43				215	93	430	143	646			560
Changes in operating assets and liabilities:
Accounts receivable									43				35	(42)	(71)	3,008	72			450
Finance receivables, net									397				0	(626)	0	(2,912)	(67)			1,287
Sale of finance receivables																2,051
Inventory, net									(252)				(490)	(1,793)	(714)	(2,153)	(915)			(2,064)
Prepaid expenses and other current assets									114				100	604	100	919	(48)			457
Accounts payable and accrued expenses									678				632	754	1,140	1,447	2,501
Deferred revenue									171				(59)	570	326	536	157			115
Income taxes payable									(55)				7	(80)	15	(30)	22			0
Net cash (used in) provided by operating activities									(284)				350	(2,229)	997	(1,021)	1,480			699
INVESTING ACTIVITIES:
Purchase of property and equipment, including rentals									272				187	33	192	(133)	282			254
Proceeds from sale of property and equipment									0					0	0	0	0			0
Cash paid for acquisitions, net of cash acquired														0		0
Net cash used in investing activities									272				187	33	192	(133)	282			254
FINANCING ACTIVITIES:
Proceeds from collateralized borrowing from the transfer of finance receivables														1,075		1,075
Cash used in retirement of common stock													0		0	0	0			0
Proceeds from exercise of common stock warrants													0		0		0			0
Payment of debt issuance costs														0		0	0			0
Proceeds from exercise of common stock options																0
Proceeds from issuance of long-term debt														0		0
Proceeds from revolving credit facility														0		0
Repayment of revolving credit facility																0
Issuance of common stock in public offering, net									0					0		0
Repayment of line of credit														0	(106)	0	(106)			0
Repayment of capital lease obligations and long-term debt									12				(537)	1,095	(1,083)	27	(1,656)			(953)
Net cash (used in) provided by financing activities									12				(537)	2,170	(1,189)	1,102	(1,762)			(953)
Net (decrease) increase in cash and cash equivalents									0				0	(26)	0	(52)	0			0
Cash and cash equivalents at beginning of year						$ (52)	(26)	0	0	0	0	0	0	0	0	0	0		$ 0	0	$ 0
Cash and cash equivalents at end of year	$ (26)						$ (52)	$ (26)	$ 0	$ 0	$ 0	$ 0	$ 0	$ (26)	$ 0	$ (52)	$ 0			$ 0