| Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
|---|---|---|---|
| Mar. 31, 2021 | Mar. 31, 2020 | Mar. 31, 2019 | |
| Reserve for Doubtful Accounts Receivable [Member] | |||
| Valuation and Qualifying Accounts Disclosure [Line Items] | |||
| Balance at Beginning of Period | $ 33 | $ 33 | $ 339 | 
| Charged to Costs and Expenses | (4) | (167) | |
| Charged to Other Accounts | (13) | ||
| Deductions | (126) | ||
| Balance at End of Period | 29 | 33 | 33 | 
| Product Warranty Liability [Member] | |||
| Valuation and Qualifying Accounts Disclosure [Line Items] | |||
| Balance at Beginning of Period | 359 | 366 | 493 | 
| Charged to Costs and Expenses | 344 | 62 | 234 | 
| Charged to Other Accounts | (85) | ||
| Deductions | (77) | (69) | (276) | 
| Balance at End of Period | $ 626 | $ 359 | 366 | 
| Restructuring Reserve [Member] | |||
| Valuation and Qualifying Accounts Disclosure [Line Items] | |||
| Balance at Beginning of Period | 18 | ||
| Deductions | $ (18) | ||
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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- Definition Amount of valuation and qualifying accounts and reserves. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount of increase in valuation and qualifying accounts and reserves from charge to cost and expense. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount of increase in valuation and qualifying accounts and reserves from charge to accounts other than cost and expense. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount of decrease in valuation and qualifying accounts and reserves. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Details 
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- Details 
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- Details 
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