Restructuring - Narrative (Details) $ in Thousands	12 Months Ended
	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($) employee	Mar. 31, 2015 USD ($) workers
Restructuring Cost and Reserve [Line Items]
Document Period End Date	Mar. 31, 2017
Restructuring charges	$ 5,404	$ 4,178	$ 13,017
Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	3,190	2,375	2,672
Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	2,214	$ 1,803	10,345
Restructuring and Related Cost, Expected Number of Positions Eliminated | employee		50
Restructuring and Related Cost, Number of Positions Eliminated, Inception to Date | employee		24
Solid Capacitors
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,333	$ 1,916	3,297
Film and Electrolytic
Restructuring Cost and Reserve [Line Items]
Restructuring charges	3,738	1,714	8,221
Film and Electrolytic | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	600
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring charges	333	548	1,499
FLORIDA | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	300
SOUTH CAROLINA | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	100
SOUTH CAROLINA | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	300
United Kingdom | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	200
Mexico | Solid Capacitors | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	600
Mexico | Solid Capacitors | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	300	900	1,900
Mexico | K-Salt [Member] | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	100
TENNESSEE | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,900
TENNESSEE | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	400
Europe and Asia [Member] | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges			500
Victoria Mexico [Member] | Solid Capacitors | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		400
Victoria Mexico [Member] | Solid Capacitors | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		500
Europe and North America [Member] | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		500	1,100
Europe [Member] | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	300		$ 4,100
Europe [Member] | Film and Electrolytic | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		300
SWEDEN | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 300
Italy | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Number of Positions Eliminated | workers			50
Italy | Film and Electrolytic | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 3,200
Restructuring Reserve, Accrual Adjustment		(1,000)
China | Film and Electrolytic | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		400
China | Film and Electrolytic | Personnel reduction costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		600
Europe North America and Asia [Domain] | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		500
Mexico and Macedonia [Member] | Film and Electrolytic | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges			300
Landsberg Germany [Member] | Film and Electrolytic | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 1,100	400
Portugal | Solid Capacitors | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 1,400