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Basis of Presentation and Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands |  | 1 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
Nov. 29, 2019 | Jan. 31, 2020 | Oct. 31, 2019 | Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2016 | Jun. 30, 2020 | Jun. 30, 2019 | Dec. 31, 2019
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Securities excluded from net loss per share calculation (in shares) |  |  |  | 47,000 | 28,000 |  | 4,000 | 66,000 |
Sale of common stock (in shares) |  |  |  |  |  |  | 721,546 |  |
Exercise price of common stock (in dollars per share) |  |  |  | $ 3.48 |  |  | $ 3.48 |  |
Proceeds from issuance of warrants |  |  |  |  |  |  | $ 2,500 |  |
Issuance of warrants, January 2020 |  | $ 1,636 |  | $ 103 |  |  | 15 |  |
Proceeds from the exercise of warrants |  |  |  |  |  |  | 51 | $ 0 |
Amount paid for clearing fees |  | 231 |  |  |  |  |  |  |
Offering costs |  | 474 |  |  |  |  |  |  |
Proceeds from sale of common stock |  | $ 2,300 |  |  |  |  |  |  |
Percentage of gross proceeds used to make payments on note |  | 10.00% |  |  |  |  |  |  |
Gross proceeds |  | $ 275 |  |  |  |  |  |  |
Payments on the Iliad Note |  |  |  |  |  |  | $ 526 | $ 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 |  |  |  |  |  |  |
Institutional Investor |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Sale of common stock (in shares) |  | 688,360 |  | 673,361 |  |  |  |  |
Exercise price of common stock (in dollars per share) |  |  |  | $ 3.37 |  |  | $ 3.37 |  |
Purchase price (in usd per share) |  | $ 0.625 |  |  |  |  |  |  |
Private Placement |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Sale of common stock (in shares) |  |  |  | 48,185 |  |  | 48,185 |  |
Exercise price of common stock (in dollars per share) |  |  |  | $ 4.9940 |  |  | $ 4.9940 |  |
Amount paid for placement agent commissions |  | $ 193 |  |  |  |  |  |  |
Amount paid related to expenses for registered direct offering and concurrent private placement |  | $ 50 |  |  |  |  |  |  |
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 |  |  |  |  |  |
Minimum |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Warranty service periods |  |  |  |  |  | 1 year |  |  |
Maximum |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Warranty service periods |  |  |  |  |  | 5 years |  |  |
Maximum | Commercial LEDFL Tubular LED Lamps (Excluding Battery Backup TLED), Troffer Luminaires, And Certain Globe Lights |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Warranty service periods |  |  |  |  |  | 10 years |  |  |
Customer concentration risk |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  | 10.00% |  |  | 10.00% |  |
Customer concentration risk | Revenue | Distributor To The U.S. Navy |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  | 40.00% | 13.00% |  | 39.00% | 17.00% |
Customer concentration risk | Revenue | Distributor for the U.S. Navy and a Regional Commercial Lighting Retrofit Company |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  | 15.00% | 26.00% |  | 15.00% | 28.00% |
Customer concentration risk | Revenue | U.S. Navy and Shipbuilders |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  | 11.00% | 20.00% |  | 53.00% | 26.00% |
Customer concentration risk | Revenue | Distributor To The U.S. Navy Combined With Sales To Shipbuilders |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  | 60.00% |  |  |  |  |
Customer concentration risk | Accounts receivable | Distributor To The U.S. Navy |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  |  |  |  | 47.00% |  | 10.00%
Customer concentration risk | Accounts receivable | Distributor for the U.S. Navy and a Regional Commercial Lighting Retrofit Company |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  |  |  |  | 19.00% |  | 41.00%
Geographic concentration risk | Revenue | Countries outside of the United States |  |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |  |
Concentration risk (less than for one percent) |  |  |  | 1.00% | 0.00% |  | 1.00% | 1.00% |

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