Restructuring Charges (Details) $ in Thousands	3 Months Ended			6 Months Ended
	Sep. 30, 2016 USD ($) employee	Sep. 30, 2015 USD ($)	Dec. 31, 2014 employee	Sep. 30, 2016 USD ($) employee	Sep. 30, 2015 USD ($)
Restructuring Charges
Restructuring charges	$ 3,998	$ 23		$ 4,686	$ 1,847
Reconciliation of restructuring liability
Costs charged to expense	3,998	23		4,686	1,847
Employee Severance
Restructuring Charges
Restructuring charges	$ 1,432	(434)		$ 2,079	1,110
Expected number of positions eliminated | employee			50
Number of positions eliminated, inception to date | employee	24			24
Reconciliation of restructuring liability
Beginning of period	$ 1,079	6,555		$ 976	7,239
Costs charged to expense	1,432	(434)		2,079	1,110
Costs paid or settled	(408)	(3,843)		(931)	(6,283)
Change in foreign exchange	(2)	2		(23)	214
End of period	2,101	2,280		2,101	2,280
Employee Severance | Tennessee
Restructuring Charges
Restructuring charges	400			400
Reconciliation of restructuring liability
Costs charged to expense	400			400
Employee Severance | Mexico | Solid Capacitors
Restructuring Charges
Restructuring charges	400	500		500	800
Reconciliation of restructuring liability
Costs charged to expense	400	500		500	800
Employee Severance | Mexico | K-Salt
Restructuring Charges
Restructuring charges	100			100
Reconciliation of restructuring liability
Costs charged to expense	100			100
Employee Severance | Florida
Restructuring Charges
Restructuring charges	300			300
Reconciliation of restructuring liability
Costs charged to expense	300			300
Employee Severance | England
Restructuring Charges
Restructuring charges	200			200
Reconciliation of restructuring liability
Costs charged to expense	200			200
Employee Severance | Sweden
Restructuring Charges
Restructuring charges				300
Reconciliation of restructuring liability
Costs charged to expense				300
Employee Severance | Europe
Restructuring Charges
Restructuring charges				200	400
Reconciliation of restructuring liability
Costs charged to expense				200	400
Employee Severance | Italy
Restructuring Charges
Restructuring accrual adjustment		(1,200)			(1,200)
Employee Severance | Europe and North America
Restructuring Charges
Restructuring charges		200			400
Reconciliation of restructuring liability
Costs charged to expense		200			400
Employee Severance | China | Film and Electrolytic
Restructuring Charges
Restructuring charges					600
Reconciliation of restructuring liability
Costs charged to expense					600
Manufacturing Relocation
Restructuring Charges
Restructuring charges	2,566	457		2,607	737
Reconciliation of restructuring liability
Beginning of period	0	0		0	0
Costs charged to expense	2,566	457		2,607	737
Costs paid or settled	(584)	(457)		(625)	(737)
Change in foreign exchange	0	0		0	0
End of period	1,982	$ 0		1,982	$ 0
Manufacturing Relocation | Film and Electrolytic
Restructuring Charges
Restructuring charges	300			300
Reconciliation of restructuring liability
Costs charged to expense	300			300
Manufacturing Relocation | Tennessee
Restructuring Charges
Restructuring charges	2,200			2,200
Reconciliation of restructuring liability
Costs charged to expense	2,200			2,200
Manufacturing Relocation | South Carolina
Restructuring Charges
Restructuring charges	100			100
Reconciliation of restructuring liability
Costs charged to expense	$ 100			$ 100