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Basis of Presentation and Summary of Significant Accounting Policies - Certain Risks and Concentrations (Details) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020
Customer concentration risk | Distributor To The U.S. Navy | Revenue |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk (less than for geographic concentration risk) | 19.00% | 67.00% | 33.00% | 52.00% |
Customer concentration risk | Distributor To The U.S. Navy | Accounts receivable |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk (less than for geographic concentration risk) |  |  | 12.00% |  | 28.00%
Customer concentration risk | Shipbuilder For U.S. Navy | Revenue |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk (less than for geographic concentration risk) | 17.00% |  | 10.00% |  |
Customer concentration risk | Shipbuilder For U.S. Navy | Accounts receivable |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk (less than for geographic concentration risk) |  |  | 27.00% |  | 21.00%
Customer concentration risk | Regional Commercial Lighting Retrofit Company | Revenue |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk (less than for geographic concentration risk) | 27.00% | 12.00% | 17.00% | 14.00% |
Customer concentration risk | Regional Commercial Lighting Retrofit Company | Accounts receivable |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk (less than for geographic concentration risk) |  |  | 34.00% |  |
Customer concentration risk | Distributor To The U.S. Navy Combined With Sales To Shipbuilders | Revenue |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk (less than for geographic concentration risk) | 36.00% | 68.00% | 43.00% | 58.00% |
Supplier concentration risk | Offshore Supplier | Accounts Payable |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk (less than for geographic concentration risk) |  |  | 63.00% |  | 44.00%
Supplier concentration risk | Offshore Supplier | Total Expenditures |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk (less than for geographic concentration risk) | 19.00% | 25.00% | 30.00% | 19.00% |
Supplier concentration risk | Domestic Supplier | Total Expenditures |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk (less than for geographic concentration risk) |  | 20.00% |  | 14.00% |
Geographic concentration risk | Revenue | Countries outside of the United States |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk (less than for geographic concentration risk) | 1.00% | 0.00% | 1.00% | 0.00% |

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