Annual report pursuant to Section 13 and 15(d)

Income Taxes Income Taxes - Narrative (Details)

v3.19.1
Income Taxes Income Taxes - Narrative (Details) - USD ($)
12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Mar. 31, 2017
Mar. 31, 2016
Operating Loss Carryforwards [Line Items]        
Valuation allowance, deferred tax asset, increase (decrease), amount $ 112,700,000 $ 7,500,000 $ 7,000,000  
Change in U.S. valuation allowance (67,761,000) (66,948,000) (7,080,000)  
Expired foreign tax credits 0 407,000 4,766,000  
Deferred tax assets, valuation allowance 58,658,000 171,401,000    
Deferred tax liabilities, unremitted foreign earnings 0      
Unrecognized tax benefits 7,661,000 8,680,000 7,390,000 $ 7,103,000
Unrecognized tax benefits that would impact effective tax rate 1,900,000      
Amount of unrecorded benefit 1,000,000      
Income tax penalties and interest accrued 500,000 900,000    
Net foreign taxable income reported on prior year federal income tax return 34,300,000      
Tax Cuts & Jobs Act 800,000      
Income tax expense (benefit) (1) $ (39,460,000) $ 9,132,000 $ 4,294,000  
Macedonia        
Operating Loss Carryforwards [Line Items]        
Statutory tax rate, percent 0.00% 10.00% 10.00%  
THAILAND        
Operating Loss Carryforwards [Line Items]        
Statutory tax rate, percent 0.00% 20.00%    
Valuation Allowance for Deferred Tax Assets        
Operating Loss Carryforwards [Line Items]        
Valuation allowances and reserves $ 58,658,000 $ 171,401,000 $ 163,898,000 $ 170,917,000
Foreign Tax Authority        
Operating Loss Carryforwards [Line Items]        
Valuation allowance, deferred tax asset, increase (decrease), amount 44,900,000 74,400,000    
Operating loss carryforwards 135,300,000      
Operating loss carryforwards subject to expiration within one year 0      
Foreign Tax Authority | TOKIN        
Operating Loss Carryforwards [Line Items]        
Valuation allowance, deferred tax asset, increase (decrease), amount   78,200,000    
Foreign Tax Authority | Changes in Temporary Differences and Net Operating Utilizations of Deferred Tax Assets        
Operating Loss Carryforwards [Line Items]        
Valuation allowance, deferred tax asset, increase (decrease), amount (35,500,000)      
Foreign Tax Authority | Release of Valuation Allowance of Deferred Tax Assets        
Operating Loss Carryforwards [Line Items]        
Valuation allowance, deferred tax asset, increase (decrease), amount $ (5,500,000)      
Foreign Tax Authority | Other Foreign Operations        
Operating Loss Carryforwards [Line Items]        
Valuation allowance, deferred tax asset, increase (decrease), amount   (3,800,000)    
Domestic Tax Authority        
Operating Loss Carryforwards [Line Items]        
Valuation allowance, deferred tax asset, increase (decrease), amount     $ 1,200,000  
Other information pertaining to income taxes 227.1      
Operating loss carryforwards $ 114,300,000      
Deferred tax assets, valuation allowance 16,900,000      
Domestic Tax Authority | TOKIN        
Operating Loss Carryforwards [Line Items]        
Valuation allowance, deferred tax asset, increase (decrease), amount   (21,100,000)    
Domestic Tax Authority | Release of Valuation Allowance of Deferred Tax Assets        
Operating Loss Carryforwards [Line Items]        
Valuation allowance, deferred tax asset, increase (decrease), amount (44,200,000)      
Domestic Tax Authority | Operating Loss Carryforwards of Deferred Tax Assets        
Operating Loss Carryforwards [Line Items]        
Valuation allowance, deferred tax asset, increase (decrease), amount (26,900,000)      
Domestic Tax Authority | Deferred Tax Assets under U.S. Tax Reform        
Operating Loss Carryforwards [Line Items]        
Valuation allowance, deferred tax asset, increase (decrease), amount   (49,400,000)    
State and Local Jurisdiction        
Operating Loss Carryforwards [Line Items]        
Operating loss carryforwards 525,100,000      
Operating loss carryforwards subject to expiration within one year $ 3,600,000      
Operating loss carryforwards, expiration period 1 year      
Macedonia        
Operating Loss Carryforwards [Line Items]        
Income tax holiday, aggregate dollar amount $ 0      
Reduction in Taxes [Member]        
Operating Loss Carryforwards [Line Items]        
Income tax expense (benefit) (1)   $ 800,000