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Revenue Recognition - Additional Information (Detail) - USD ($) | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Mar. 31, 2020 | Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2020 | Mar. 31, 2019 | Mar. 31, 2018 | Apr. 01, 2018
Contract With Customer Assets And Liabilities [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Net sales | $ 23,082,000 | $ 25,286,000 | $ 21,643,000 | $ 20,593,000 | $ 23,641,000 | $ 17,198,000 | $ 21,441,000 | $ 29,551,000 | $ 90,604,000 | $ 91,831,000 | $ 77,534,000 |
Percentage of revenue from contracts recognized over time |  |  |  |  |  |  |  |  | 70.00% |  |  |
Percentage of revenue from contracts recognized upon shipment |  |  |  |  |  |  |  |  | 30.00% |  |  |
Revenue recognized included in contract liability |  |  |  |  |  |  |  |  | $ 17,040,000 |  |  |
Unbilled revenue (contract assets) |  |  |  |  |  |  |  |  | 7,070,000 |  |  |
Contract with customer liability increase in contract asset due to contract progress. |  |  |  |  |  |  |  |  | 20,585,000 |  |  |
Contract with customer liability offset by invoicing to customers. |  |  |  |  |  |  |  |  | 13,515,000 |  |  |
Customer deposits, current |  |  |  |  |  |  |  |  | 3,864,000 |  |  |
Contract with customer liability offset by new customer deposits |  |  |  |  |  |  |  |  | 13,176,000 |  |  |
Receivables billed but not paid under retainage provisions in its customer contracts | 2,016,000 |  |  |  | 2,214,000 |  |  |  | 2,016,000 | 2,214,000 |  |
Amortization expense |  |  |  |  |  |  |  |  | 169,000 |  |  |
Revenue remaining unsatisfied performance obligations amount | 112,389,000 |  |  |  |  |  |  |  | 112,389,000 |  |  |
Customer Deposit [Member] |  |  |  |  |  |  |  |  |  |  |  |
Contract With Customer Assets And Liabilities [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Contract liabilities | 3,660,000 |  |  |  |  |  |  |  | 3,660,000 |  |  | $ 6,382,000
Prepaid Expenses and Other Current Assets [Member] |  |  |  |  |  |  |  |  |  |  |  |
Contract With Customer Assets And Liabilities [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Capitalized costs, net of amortization | $ 45,000 |  |  |  | $ 133,000 |  |  |  | 45,000 | 133,000 |  |
Sudan [Member] |  |  |  |  |  |  |  |  |  |  |  |
Contract With Customer Assets And Liabilities [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Net sales |  |  |  |  |  |  |  |  | 0 | 0 | 0 |
Iran [Member] |  |  |  |  |  |  |  |  |  |  |  |
Contract With Customer Assets And Liabilities [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Net sales |  |  |  |  |  |  |  |  | 0 | 0 | 0 |
Syria [Member] |  |  |  |  |  |  |  |  |  |  |  |
Contract With Customer Assets And Liabilities [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Net sales |  |  |  |  |  |  |  |  | $ 0 | $ 0 | $ 0 |

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