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Basis of Presentation and Summary of Significant Accounting Policies - Narrative (Details) - USD ($) |  | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
Nov. 29, 2019 | Jan. 31, 2020 | Oct. 31, 2019 | Sep. 30, 2020 | Jun. 30, 2020 | Sep. 30, 2019 | Mar. 31, 2016 | Sep. 30, 2020 | Sep. 30, 2019 | Dec. 31, 2019
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Sale of common stock (in shares) |  |  |  |  |  |  |  | 539,152 |  |
Exercise price of common stock (in dollars per share) |  |  |  | $ 3.50 |  |  |  | $ 3.50 |  |
Proceeds from issuance of warrants |  |  |  |  |  |  |  | $ 1,900,000 |  |
Issuance of warrants, January 2020 |  |  |  | $ 1,555,000 | $ 103,000 |  |  | 197,394 |  |
Proceeds from the exercise of warrants |  |  |  |  |  |  |  | 676,000 | $ 0 |
Amount paid for clearing fees |  | $ 231,000 |  |  |  |  |  |  |  |
Offering costs |  | 474,000 |  |  |  |  |  |  |  |
Proceeds from sale of common stock |  | $ 2,300,000 |  |  |  |  |  |  |  |
Percentage of gross proceeds used to make payments on note |  | 10.00% |  |  |  |  |  |  |  |
Gross proceeds |  | $ 275,000 |  |  |  |  |  |  |  |
Payments on the Iliad Note |  |  |  |  |  |  |  | $ 976,000 | $ 0 |
Note Purchase Agreement |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Percentage of gross proceeds used to make payments on note | 10.00% |  |  |  |  |  |  |  |  |
Payments on the Iliad Note |  | $ 226,000 |  |  |  |  |  |  |  |
Institutional Investor |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Sale of common stock (in shares) |  | 688,360 |  | 497,472 |  |  |  |  |  |
Exercise price of common stock (in dollars per share) |  | $ 3.37 |  |  |  |  |  |  |  |
Purchase price (in usd per share) |  | 0.625 |  |  |  |  |  |  |  |
Private Placement |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Sale of common stock (in shares) |  |  |  | 41,680 |  |  |  | 48,185 |  |
Exercise price of common stock (in dollars per share) |  | $ 4.99 |  | $ 4.9940 |  |  |  | $ 4.9940 |  |
Amount paid for placement agent commissions |  | $ 193,000 |  |  |  |  |  |  |  |
Amount paid related to expenses for registered direct offering and concurrent private placement |  | $ 50,000 |  |  |  |  |  |  |  |
All Other Products |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Warranty service periods |  |  | 5 years |  |  |  |  |  |  |
LEDFL Tubular LED Lamps (Excluding Red Caps) |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Warranty service periods |  |  | 10 years |  |  |  |  |  |  |
Common Stock |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Securities excluded from net loss per share calculation (in shares) |  |  |  |  |  | 0 |  |  |  |
Equity Option |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Securities excluded from net loss per share calculation (in shares) |  |  |  | 117,000 |  |  |  | 57,000 | 0 |
Restricted Stock Units |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Securities excluded from net loss per share calculation (in shares) |  |  |  | 13,000 |  |  |  | 7,000 | 31,000 |
Warrant |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Securities excluded from net loss per share calculation (in shares) |  |  |  | 321,000 |  |  |  | 152,000 | 507,000 |
Convertible securities |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Securities excluded from net loss per share calculation (in shares) |  |  |  | 519,000 |  | 514,000 |  | 531,000 |  |
Minimum |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Warranty service periods |  |  |  |  |  |  | 1 year |  |  |
Maximum |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Warranty service periods |  |  |  |  |  |  | 5 years |  |  |
Customer concentration risk |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  | 10.00% |  |  |  | 10.00% |  |
Customer concentration risk | Distributor To The U.S. Navy | Revenue |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  | 67.00% |  | 27.00% |  | 52.00% | 20.00% |
Customer concentration risk | Distributor To The U.S. Navy | Accounts receivable |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  |  |  |  |  | 73.00% |  | 10.00%
Customer concentration risk | Distributor for the U.S. Navy and a Regional Commercial Lighting Retrofit Company | Revenue |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  | 12.00% |  | 14.00% |  | 14.00% | 23.00% |
Customer concentration risk | Distributor for the U.S. Navy and a Regional Commercial Lighting Retrofit Company | Accounts receivable |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  |  |  |  |  |  |  | 41.00%
Customer concentration risk | U.S. Navy and Shipbuilders | Revenue |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  |  |  | 30.00% |  | 58.00% | 27.00% |
Customer concentration risk | Global Healthcare Provider | Revenue |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  |  |  | 15.00% |  |  |  |
Customer concentration risk | Distributor To The U.S. Navy Combined With Sales To Shipbuilders | Revenue |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  | 68.00% |  |  |  |  |  |
Customer concentration risk | Two Offshore Suppliers | Accounts receivable | Minimum |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  | 20.00% |  |  |  | 14.00% |  |
Customer concentration risk | Two Offshore Suppliers | Accounts receivable | Maximum |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  | 25.00% |  |  |  | 19.00% |  |
Customer concentration risk | Two Offshore Suppliers | Accounts Payable | Minimum |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  |  |  |  |  | 24.00% |  |
Customer concentration risk | Two Offshore Suppliers | Accounts Payable | Maximum |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  |  |  |  |  | 35.00% |  |
Customer concentration risk | One Offshore Supplier | Accounts receivable |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  |  |  | 18.00% |  |  | 20.00% |
Customer concentration risk | One Offshore Supplier | Accounts Payable |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  |  |  |  |  | 36.70% |  |
Customer concentration risk | One Domestic Supplier | Accounts Payable |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  |  |  |  |  | 16.00% |  |
Geographic concentration risk | Revenue | Countries outside of the United States |  |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  |  |  | 0.00% |  |  | 1.00% |

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