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Summary of Significant Accounting Policies - Concentration Risk (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Concentration Risk [Line Items] |  |
Short-term deposits | $ 0.8 | $ 0.1
Net sales | Customer concentration risk |  |
Concentration Risk [Line Items] |  |
Concentration risk | 62.00% | 45.00%
Distributor To The U.S. Navy | Net sales | Customer concentration risk |  |
Concentration Risk [Line Items] |  |
Concentration risk | 49.00% | 23.00%
Distributor To The U.S. Navy | Accounts receivable |  |
Concentration Risk [Line Items] |  |
Concentration risk | 28.00% |
Distributor To The U.S. Navy | Accounts receivable | Customer concentration risk |  |
Concentration Risk [Line Items] |  |
Concentration risk |  | 10.00%
Regional Commercial Lighting Retrofit Company | Net sales | Customer concentration risk |  |
Concentration Risk [Line Items] |  |
Concentration risk | 12.00% |
Regional Commercial Lighting Retrofit Company | Accounts receivable |  |
Concentration Risk [Line Items] |  |
Concentration risk |  | 41.00%
Distributor To U.S. Navy Combined With Sales To Shipbuilders | Net sales | Customer concentration risk |  |
Concentration Risk [Line Items] |  |
Concentration risk | 53.00% |
Shipbuilder For U.S. Navy | Accounts receivable |  |
Concentration Risk [Line Items] |  |
Concentration risk | 21.00% |
Offshore Supplier | Accounts receivable | Customer concentration risk |  |
Concentration Risk [Line Items] |  |
Concentration risk | 21.00% | 21.00%
Offshore Supplier | Accounts Payable | Customer concentration risk |  |
Concentration Risk [Line Items] |  |
Concentration risk | 44.00% | 54.00%
Domestic Supplier | Accounts receivable | Customer concentration risk |  |
Concentration Risk [Line Items] |  |
Concentration risk | 12.00% |

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