| Income Taxes - Summary of Net Deferred Income Tax Liability (Detail) - USD ($) $ in Thousands | Mar. 31, 2021 | Mar. 31, 2020 | 
|---|---|---|
| Components Of Deferred Tax Assets And Liabilities [Abstract] | ||
| Depreciation | $ (1,772) | $ (1,707) | 
| Accrued compensation | 147 | 206 | 
| Prepaid pension asset | (1,386) | (783) | 
| Accrued pension liability | 347 | 169 | 
| Accrued postretirement benefits | 131 | 143 | 
| Compensated absences | 435 | 402 | 
| Inventories | 462 | (13) | 
| Warranty liability | 140 | 81 | 
| Accrued expenses | 585 | 366 | 
| Equity-based compensation | 337 | 385 | 
| Operating lease assets | (22) | (58) | 
| Operating lease liabilities | 23 | 60 | 
| New York State investment tax credit | 1,115 | 1,108 | 
| Net operating loss carryforwards | 75 | |
| Capital loss related to sale of Energy Steel | 4,211 | 4,211 | 
| Other | (62) | 1 | 
| Deferred Tax Assets, gross | 4,691 | 4,646 | 
| Less: Valuation allowance | (5,326) | (5,319) | 
| Total | $ (635) | $ (673) | 
| X | ||||||||||
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- Definition Amount of deferred tax liability attributable to taxable temporary differences from prepaid pension asset. No definition available. 
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- Definition Amount before allocation of valuation allowances of deferred tax asset (liability) attributable to deductible (taxable) temporary differences from inventory. No definition available. 
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- Definition Amount before allocation of valuation allowance of deferred tax asset (liability) attributable to deductible(taxable) temporary differences not separately disclosed. No definition available. 
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- Definition Amount of deferred tax liability attributable to taxable temporary differences from operating lease assets. No definition available. 
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| X | ||||||||||
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from operating lease liabilities. No definition available. 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from employee benefits and Long Term Incentive Plan. No definition available. 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible state investment tax credit carryforwards. No definition available. 
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| X | ||||||||||
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- References No definition available. 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible capital loss carryforwards. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from compensated absences (includes, but not limited to, sick and personal days). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from pension benefits. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from postretirement benefits. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from accrued liabilities. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from warranty reserves. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences without jurisdictional netting. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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