Quarterly report pursuant to Section 13 or 15(d)

Equity Method Investments - Equity Method Investment Reconciliation (Details)

v3.10.0.1
Equity Method Investments - Equity Method Investment Reconciliation (Details)
$ in Thousands, $ in Millions
3 Months Ended 6 Months Ended
Jul. 26, 2016
USD ($)
May 02, 2016
installment
suit
Dec. 09, 2015
USD ($)
Dec. 09, 2015
TWD ($)
Sep. 02, 2015
installment
Sep. 30, 2018
USD ($)
Sep. 30, 2017
USD ($)
Sep. 30, 2018
USD ($)
Sep. 30, 2017
USD ($)
Mar. 31, 2018
USD ($)
May 05, 2010
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity [Abstract]                      
Equity Method Investments           $ 12,215   $ 12,215   $ 12,016  
Indemnification Agreement [Member] | Equity Method Investments [Member] | NEC TOKIN Corporation [Member]                      
Related Party Transactions [Abstract]                      
Litigation Settlement, Number of Payment Installments | installment   5                  
Settled Litigation [Member] | Indemnification Agreement [Member] | Equity Method Investments [Member]                      
Related Party Transactions [Abstract]                      
Litigation Settlement, Payment Period         5 years            
Litigation Settlement, Number of Payment Installments | installment         6            
Preliminary Settlement [Member] | Indemnification Agreement [Member] | Equity Method Investments [Member] | NEC TOKIN Corporation [Member]                      
Related Party Transactions [Abstract]                      
Loss Contingency, Pending Claims, Number | suit   2                  
TAIWAN, PROVINCE OF CHINA | Taiwan, New Dollars                      
Related Party Transactions [Abstract]                      
Loss Contingency, Damages Sought, Value       $ 1,200.0              
TAIWAN, PROVINCE OF CHINA | Taiwan, New Dollars | Minimum [Member]                      
Related Party Transactions [Abstract]                      
Loss Contingency, Damages Sought, Value       $ 609.1              
TAIWAN, PROVINCE OF CHINA | United States of America, Dollars                      
Related Party Transactions [Abstract]                      
Loss Contingency, Damages Sought, Value     $ 39,900                
TAIWAN, PROVINCE OF CHINA | United States of America, Dollars | Minimum [Member]                      
Related Party Transactions [Abstract]                      
Loss Contingency, Damages Sought, Value     $ 19,900                
BRAZIL | United States of America, Dollars | Settled Litigation [Member]                      
Related Party Transactions [Abstract]                      
Loss Contingency, Damages Paid, Value $ 200                    
Senior Notes [Member]                      
Schedule of Equity Method Investments [Line Items]                      
Rate                     10.50%
NT Sales Co., Ltd (NTS) [Member]                      
Related Party Transactions [Abstract]                      
Sales to NEC TOKIN           12,389 $ 13,131 24,597 $ 25,965    
NEC TOKIN's sales to KEMET           $ 383 $ 315 $ 771 $ 724