Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended			12 Months Ended
	Jan. 01, 2019	Dec. 31, 2019	Sep. 30, 2019	Mar. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Concentration Risk [Line Items]
Cash and cash equivalents		$ 692			$ 692	$ 6,335	$ 10,761	$ 16,629
Restricted cash held		300			300	300
Provision for slow-moving and obsolete inventories					(14)	(17)	1,400
Net reduction of excess and obsolete reserves					$ 567
Payment terms					30 days
Deferred tax assets, operating loss carry-forwards		12,758			$ 12,758	10,793	8,610
Deferred tax assets, operating loss carryforwards, portion available after application of IRC Section 382 limitations		54,500			54,500
Operating loss carry-forwards		8,300			8,300	$ 8,700	$ 37,300
Deferred tax assets, tax credit carryforwards, research		300			$ 300
Antidilutive securities excluded from computation of earnings per share (number of shares)					27,883	59,180	60,434
Advertising expense					$ 200	$ 300	$ 500
Operating lease liabilities		$ 1,480			$ 1,480
Operating lease, impairment loss	$ 200
Customer concentration risk | Net sales
Concentration Risk [Line Items]
Concentration risk					45.00%	42.00%	17.00%
Customer concentration risk | Net sales | Distributor To The U.S. Navy
Concentration Risk [Line Items]
Concentration risk					23.00%		22.00%
Customer concentration risk | Net sales | Northeast Ohio Hospital [Member]
Concentration Risk [Line Items]
Concentration risk						18.00%
Customer concentration risk | Net sales | Commercial Lighting Retrofit Company
Concentration Risk [Line Items]
Concentration risk						13.00%
Customer concentration risk | Accounts receivable | Distributor To The U.S. Navy
Concentration Risk [Line Items]
Concentration risk					9.80%	40.40%
Customer concentration risk | Accounts receivable | Commercial Lighting Retrofit Company
Concentration Risk [Line Items]
Concentration risk					41.00%
Minimum
Concentration Risk [Line Items]
Property and equipment, useful life					2 years
Warranty for finished goods, number of years				1 year
Maximum
Concentration Risk [Line Items]
Property and equipment, useful life					15 years
Warranty for finished goods, number of years				5 years
Accounting Standards Update 2016-02
Concentration Risk [Line Items]
Operating lease liabilities	2,900
Commercial LEDFL Tubular LED Lamps (Excluding Battery Backup TLED), Troffer Luminaires, And Certain Globe Lights
Concentration Risk [Line Items]
Warranty for finished goods, number of years			10 years
Other LED Products
Concentration Risk [Line Items]
Warranty for finished goods, number of years		5 years	5 years
LEDFL Tubular LED Lamps (Excluding Red Caps)
Concentration Risk [Line Items]
Warranty for finished goods, number of years		10 years
2017 Restructuring Plan | Restructuring Liability
Concentration Risk [Line Items]
Adjustment of lease obligations	$ 300				$ (273)	$ 90
U.S. Federal
Concentration Risk [Line Items]
Deferred tax assets, operating loss carry-forwards		$ 108,800			108,800
State and Local
Concentration Risk [Line Items]
Deferred tax assets, operating loss carry-forwards		$ 64,500			$ 64,500