Quarterly Financial Information (Unaudited) (as restated), Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	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
Current assets: [Abstract]
Cash and cash equivalents	$ 16,487	$ 15,888	$ 14,445	$ 3,417	$ 4,069	$ 3,127	$ 3,938	$ 3,763	$ 3,928
Accounts receivable, net	3,393	2,728	2,574	2,491	3,141	3,184	3,560	3,288
Inventories	2,794	2,488	2,413	3,029	3,009	3,533	3,487	2,670
Prepaid expenses and other current assets	536	670	828	1,379	533	209	373	804
Total current assets	23,210	21,774	20,260	10,316	10,752	10,053	11,358	10,525
Property and equipment, net	5,301	5,698	6,271	6,916	7,703	8,658	9,396	9,975
Intangible assets, net	9,765	10,217	10,670	11,122	11,825	12,302	13,298	13,858	13,412
Goodwill	8,803	8,803	8,803	8,803	8,803	8,803	8,803	8,803	8,803
Other assets	428	48	48	48	48	48	47	46
Total assets	47,507	46,540	46,052	37,205	39,131	39,864	42,902	43,207	43,193
Current liabilities: [Abstract]
Note payable	0		51	252	357	34	137	239
Current portion of long-term debt	252		0	3,410	2,387	1,936	3,429	2,571
Accounts payable	1,764	1,663	1,477	2,658	2,277	1,907	2,301	2,206
Other accrued liabilities	4,500	4,247	3,754	3,541	3,581	3,233	3,359	3,266	2,909
Deferred revenues	2,099	1,877	1,802	1,725	1,871	1,952	2,210	2,132	2,230
Warrant liability		726					0
Total current liabilities	8,615	9,512	7,084	11,586	10,473	9,062	11,436	10,414	9,045
Long-term debt, net	7,145	7,362	7,321	6,869	7,853	8,842	8,150	8,948
Senior secured convertible debentures, net						0	5,587	5,274
Derivative liability senior secured convertible debentures					0	0	1,993	4,896	3,158
Deferred tax liability	111	392	493	454	414	539	479	419
Warranty liability	0	615	263	24	67	255	676	1,333	662
Other liabilities	388	269	288	649	444	412	724	752
Total liabilities	16,259	17,149	15,449	19,582	19,251	19,110	29,045	32,036	28,156
Stockholders' equity: [Abstract]
Preferred stock - Convertible Preferred Stock						4	0
Common Stock	30	30	30	4	4	3	3	2	2
Additional paid-in capital	241,988	239,040	238,673	223,848	223,829	223,780	197,810	197,583	197,475
Accumulated deficit	(210,771)	(209,683)	(208,101)	(206,233)	(203,957)	(203,035)	(183,958)	(186,417)	(182,443)
Accumulated other comprehensive income			0	0		2	2	2	2
Total stockholders' equity	31,248	29,388	30,603	17,623	19,880	20,754	13,857	11,171	15,037
Total liabilities and stockholders' equity	47,507	46,540	46,052	37,205	39,131	39,864	42,902	43,207
Series C Preferred Stock [Member]
Stockholders' equity: [Abstract]
Preferred stock - Convertible Preferred Stock	$ 1	1	1	4	4			1
Previously Reported [Member]
Current assets: [Abstract]
Cash and cash equivalents		15,888	14,445	3,417		3,127	3,938	3,763
Accounts receivable, net		2,728	2,574	2,491		3,184	3,560	3,288
Inventories		2,488	2,413	3,029		3,533	3,487	2,670
Prepaid expenses and other current assets		670	828	1,379		209	373	804
Total current assets		21,774	20,260	10,316		10,053	11,358	10,525
Property and equipment, net		5,698	6,271	6,916		8,658	9,396	9,975
Intangible assets, net		9,867	10,270	10,672	11,325	12,302	13,298	13,858	13,412
Goodwill		8,803	8,803	8,803		8,803	8,803	8,803
Other assets		48	48	48		48	47	46
Total assets		46,190	45,652	36,755	38,631	39,864	42,902	43,207	43,193
Current liabilities: [Abstract]
Note payable			51	252		34	137	239
Current portion of long-term debt			0	3,410		1,936	3,429	2,571
Accounts payable		1,663	1,477	2,658		1,907	2,301	2,206
Other accrued liabilities		2,697	2,330	2,216	2,360	1,899	2,160	2,214	1,992
Deferred revenues		327	393	440	291	350	413	334	235
Warrant liability		104					0
Total current liabilities		4,791	4,251	8,976	7,672	6,126	8,440	7,564	6,133
Long-term debt, net		7,362	7,321	6,869		8,842	8,150	8,948
Senior secured convertible debentures, net						0	13,386	12,695
Derivative liability senior secured convertible debentures					0	0	0	0	0
Deferred tax liability		392	493	454		539	479	419
Warranty liability		0	0	0	3	28	109	237	105
Other liabilities		268	287	649		412	724	752
Total liabilities		12,813	12,352	16,948	16,386	15,947	31,288	30,615	28,474
Stockholders' equity: [Abstract]
Preferred stock - Convertible Preferred Stock						4	0
Common Stock		30	30	4	4	3	3	2	2
Additional paid-in capital		266,854	266,487	251,662	251,643	251,594	225,624	225,397	225,289
Accumulated deficit		(233,508)	(233,218)	(231,863)	(229,406)	(227,686)	(214,015)	(212,810)	(210,575)
Accumulated other comprehensive income			0	0		2	2	2	2
Total stockholders' equity		33,377	33,300	19,807	22,245	23,917	11,614	12,592	14,719
Total liabilities and stockholders' equity		46,190	45,652	36,755		39,864	42,902	43,207
Previously Reported [Member] | Series C Preferred Stock [Member]
Stockholders' equity: [Abstract]
Preferred stock - Convertible Preferred Stock		1	1	4	4			1
Restatement Adjustment [Member]
Current assets: [Abstract]
Cash and cash equivalents		0	0	0		0	0	0
Total current assets		0	0	0
Intangible assets, net		400	450	500					0
Total assets		400	450	500		0	0	0	0
Current liabilities: [Abstract]
Note payable			0	0		0		0
Accounts payable		0
Other accrued liabilities		1,424	1,325	1,221		1,199	1,052	917	917
Deferred revenues		1,409	1,285	1,580		1,797	1,798	1,995	1,995
Warrant liability		108
Total current liabilities		2,941	2,610	2,801		2,996	2,850	2,912	2,912
Long-term debt, net						0	0
Senior secured convertible debentures, net						(7,799)	(7,421)	(6,945)
Derivative liability senior secured convertible debentures						1,993	4,896	3,158	3,158
Deferred tax liability						0	0
Warranty liability		155	23	64		567	1,096	557	557
Other liabilities			1
Total liabilities		3,097	2,634	2,865		(2,243)	1,421	(318)	(318)
Stockholders' equity: [Abstract]
Preferred stock - Convertible Preferred Stock						0
Common Stock						0			0
Additional paid-in capital		(27,814)	(27,814)	(27,814)		(27,814)	(27,814)	(27,814)	(27,814)
Accumulated deficit		25,117	25,630	25,449		30,057	26,393	28,132	28,132
Accumulated other comprehensive income						0			0
Total stockholders' equity		(2,697)	(2,184)	(2,365)		2,243	(1,421)	318	$ 318
Total liabilities and stockholders' equity		400	450	500		0	0	0
Sales and Use Tax [Member]
Current assets: [Abstract]
Cash and cash equivalents		0	0	0		0	0	0
Total current assets		0	0	0
Intangible assets, net					0
Total assets		0	0	0		0	0	0
Current liabilities: [Abstract]
Note payable			0	0		0		0
Accounts payable		0
Other accrued liabilities		128	99	104	304	135	147	135
Deferred revenues					0
Total current liabilities		128	99	104	304	135	147	135
Derivative liability senior secured convertible debentures					0
Total liabilities		128	99	104	304	135	147	135
Stockholders' equity: [Abstract]
Common Stock					0
Additional paid-in capital					0
Accumulated deficit		(128)	(99)	(104)	(304)	(135)	(147)	(135)
Total stockholders' equity		(128)	(99)	(104)	(304)	(135)	(147)	(135)
Total liabilities and stockholders' equity		0	0	0		0	0	0
Sales and Use Tax [Member] | Series C Preferred Stock [Member]
Stockholders' equity: [Abstract]
Preferred stock - Convertible Preferred Stock					0
Warrants [Member]
Current assets: [Abstract]
Cash and cash equivalents		0	0	0		0	0	0
Total current assets		0	0	0
Intangible assets, net					0
Total assets		0	0	0		0	0	0
Current liabilities: [Abstract]
Note payable			0	0		0		0
Accounts payable		0
Other accrued liabilities					0
Deferred revenues					0
Warrant liability		514
Total current liabilities		514	0	0			0	0
Derivative liability senior secured convertible debentures					0
Warranty liability		460	240	(40)	(493)	(340)	(529)	539
Total liabilities		974	240	(40)	(493)	(340)	(529)	539
Stockholders' equity: [Abstract]
Common Stock					0
Additional paid-in capital					0
Accumulated deficit		(974)	(240)	40	493	340	529	(539)
Total stockholders' equity		(974)	(240)	40	493	340	529	(539)
Total liabilities and stockholders' equity		0	0	0		0	0	0
Warrants [Member] | Series C Preferred Stock [Member]
Stockholders' equity: [Abstract]
Preferred stock - Convertible Preferred Stock					0
Debentures [Member]
Current assets: [Abstract]
Cash and cash equivalents		0				0	0	0
Total current assets		0
Intangible assets, net					0
Total assets		0				0	0	0
Current liabilities: [Abstract]
Note payable						0		0
Accounts payable		0
Other accrued liabilities					0
Deferred revenues					0
Total current liabilities							0	0
Senior secured convertible debentures, net						7,799	(378)	(476)
Derivative liability senior secured convertible debentures					(3,158)	(1,993)	(2,903)	1,738
Total liabilities					3,787	5,806	(3,281)	1,262
Stockholders' equity: [Abstract]
Common Stock					0
Additional paid-in capital					0
Accumulated deficit					(3,787)	(5,806)	3,281	(1,262)
Total stockholders' equity					(3,787)	(5,806)	3,281	(1,262)
Total liabilities and stockholders' equity		0				0	0	0
Debentures [Member] | Series C Preferred Stock [Member]
Stockholders' equity: [Abstract]
Preferred stock - Convertible Preferred Stock					0
Intangible Impairment [Member]
Current assets: [Abstract]
Cash and cash equivalents		0	0	0		0	0	0
Total current assets		0	0	0		0	0
Intangible assets, net		(50)	(50)	(50)	500
Total assets		(50)	(50)	(50)	500	0	0	0
Current liabilities: [Abstract]
Note payable			0	0		0		0
Accounts payable		0
Other accrued liabilities					0
Deferred revenues					0
Total current liabilities			0	0		0	0	0
Derivative liability senior secured convertible debentures					0
Total liabilities		0	0	0	0	0	0	0
Stockholders' equity: [Abstract]
Common Stock					0
Additional paid-in capital					0
Accumulated deficit		(50)	(50)	(50)	500	0
Total stockholders' equity		(50)	(50)	(50)	500	0	0	0
Total liabilities and stockholders' equity		(50)	(50)	(50)		0	0	0
Intangible Impairment [Member] | Series C Preferred Stock [Member]
Stockholders' equity: [Abstract]
Preferred stock - Convertible Preferred Stock					0
Deferred Revenue [Member]
Current assets: [Abstract]
Cash and cash equivalents		0	0	0		0	0	0
Total current assets		0	0	0
Intangible assets, net					0
Total assets		0	0	0		0	0	0
Current liabilities: [Abstract]
Note payable			0	0		0		0
Accounts payable		0
Other accrued liabilities					0
Deferred revenues		140	124	(295)	(415)	(195)	(1)	(197)
Total current liabilities		140	124	(295)	(415)	(195)	(1)	(197)
Derivative liability senior secured convertible debentures					0
Warranty liability					0
Total liabilities		140	101	(295)	(415)	(195)	(1)	(197)
Stockholders' equity: [Abstract]
Common Stock					0
Additional paid-in capital					0
Accumulated deficit		(140)	(124)	295	415	195	1	197
Total stockholders' equity		(140)	(124)	295	415	195	1	197
Total liabilities and stockholders' equity		$ 0	$ 0	$ 0		$ 0	$ 0	$ 0
Deferred Revenue [Member] | Series C Preferred Stock [Member]
Stockholders' equity: [Abstract]
Preferred stock - Convertible Preferred Stock					$ 0