Annual report pursuant to Section 13 and 15(d)

(Gain) Loss on Write-Down and Disposal of Long-Lived Assets Impairment Charges - Narrative (Details)

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(Gain) Loss on Write-Down and Disposal of Long-Lived Assets Impairment Charges - Narrative (Details) - USD ($)
$ in Thousands
12 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Mar. 31, 2018
Property, Plant and Equipment [Line Items]      
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property $ (800) $ 1,000 $ 1,200
Proceeds from sale of discontinued operations     3,400
Gain (Loss) on Sale of Properties     1,900
Cost of sales 840,066 924,276 860,744
Asset Impairment Charges 18,900 700 200
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down 19,710 1,660 (992)
Corporate      
Property, Plant and Equipment [Line Items]      
Asset Impairment Charges 8,900    
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down 10,392 1,518 403
Solid Capacitors      
Property, Plant and Equipment [Line Items]      
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property     (600)
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down 1,538 235 689
Film and Electrolytic      
Property, Plant and Equipment [Line Items]      
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property     (3,600)
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down 7,780 (93) (3,356)
KFM [Member]      
Property, Plant and Equipment [Line Items]      
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property     (1,400)
Electro-magnetic, Sensors & Actuators [Member]      
Property, Plant and Equipment [Line Items]      
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property     (1,300)
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down 0 0 1,272
Machinery and equipment | Solid Capacitors      
Property, Plant and Equipment [Line Items]      
Asset Impairment Charges 1,400    
Machinery and equipment | Film and Electrolytic      
Property, Plant and Equipment [Line Items]      
Asset Impairment Charges 6,100    
Buildings | Corporate      
Property, Plant and Equipment [Line Items]      
Asset Impairment Charges 800    
Buildings | Film and Electrolytic      
Property, Plant and Equipment [Line Items]      
Asset Impairment Charges $ 900    
TOKIN | Land      
Property, Plant and Equipment [Line Items]      
Asset Impairment Charges   500  
TOKIN | Machinery and equipment      
Property, Plant and Equipment [Line Items]      
Asset Impairment Charges   $ 200  
Real Estate      
Property, Plant and Equipment [Line Items]      
Cost of sales     $ 200