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 ($)
12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Mar. 31, 2017
Property, Plant and Equipment [Line Items]      
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property $ (700,000) $ 1,200,000 $ (400,000)
Proceeds from sale of discontinued operations   3,400,000  
Gain (Loss) on Sale of Properties   1,900,000  
Cost of Real Estate Sales   200,000  
Write down of long-lived assets    
Asset Impairment Charges 1,000,000 184,000 10,300,000
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down 1,660,000 (992,000) 10,671,000
Solid Capacitors      
Property, Plant and Equipment [Line Items]      
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property   (600,000)  
Asset Impairment Charges     2,100,000
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down 235,000 689,000 2,303,000
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   (3,600,000)  
Asset Impairment Charges     8,200,000
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down (93,000) (3,356,000) 8,339,000
KFM [Member]      
Property, Plant and Equipment [Line Items]      
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property   (1,400,000)  
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   (1,300,000)  
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down 0 $ 1,272,000 0
TENNESSEE | Film and Electrolytic      
Property, Plant and Equipment [Line Items]      
Asset Impairment Charges     4,100,000
Impairment of Long-Lived Assets to be Disposed of     3,000,000
Impairment of Intangible Assets (Excluding Goodwill)     1,100,000
Italy | Film and Electrolytic      
Property, Plant and Equipment [Line Items]      
Asset Impairment Charges     $ 4,100,000
TOKIN | Land      
Property, Plant and Equipment [Line Items]      
Asset Impairment Charges 500,000    
TOKIN | Machinery and equipment      
Property, Plant and Equipment [Line Items]      
Asset Impairment Charges $ 200,000