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Revenue Recognition - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2018 | Apr. 01, 2018 | Mar. 31, 2018
Contract With Customer Assets And Liabilities [Line Items] |  |  |  |
Percentage of revenue from contracts recognized over time | 35.00% | 35.00% |  |
Percentage of revenue from contracts recognized upon shipment | 65.00% | 65.00% |  |
Revenue recognized included in contract liability | $ 2,674 | $ 8,926 |  |
Unbilled revenue (contract assets) |  | 4,490 |  |
Contract with customer liability increase in contract asset due to contract progress. |  | 7,596 |  |
Contract with customer liability offset by invoicing to customers. |  | 3,106 |  |
Customer deposits, current |  | 3,954 |  |
Contract with customer liability offset by new customer deposits. | 12,880 | 12,880 |  |
Receivables billed but not paid under retainage provisions in its customer contracts | 938 | 938 |  | $ 1,124
Amortization expense | 42 | 82 |  |
Revenue remaining unsatisfied performance obligations amount | 127,796 | 127,796 |  |
Customer Deposit [Member] |  |  |  |
Contract With Customer Assets And Liabilities [Line Items] |  |  |  |
Contract liabilities | 5,571 | 5,571 | $ 2,220 |
Prepaid Expenses and Other Current Assets [Member] |  |  |  |
Contract With Customer Assets And Liabilities [Line Items] |  |  |  |
Capitalized costs, net of amortization | $ 141 | $ 141 | $ 118 |

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