Restructuring - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 8,882	$ 8,779	$ 14,843
Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	7,618	2,823	12,587
Restructuring Reserve, Accrual Adjustment			0
Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,264	5,956	2,256
Restructuring Reserve, Accrual Adjustment			312
Employee Relocation
Restructuring Cost and Reserve [Line Items]
Restructuring charges			200
Solid Capacitors
Restructuring Cost and Reserve [Line Items]
Restructuring charges	517	4,922	983
Tantalum [Member] | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,100
Film and Electrolytic
Restructuring Cost and Reserve [Line Items]
Restructuring charges	3,458	2,717	5,788
Workforce reductions and administrative overhead			5,200
Film and Electrolytic | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	500	300
NEVADA | Solid Capacitors | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	1,107
Cumulative incurred to date	1,107
NEVADA | Solid Capacitors | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	800	3,400
NEVADA | Solid Capacitors | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	(777)
Cumulative incurred to date	2,580
TOKIN | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		900	4,400
Matamoros Mexico [Member] | K-Salt [Member] | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges			800
TENNESSEE | Employee Relocation
Restructuring Cost and Reserve [Line Items]
Restructuring charges			400
Victoria Mexico [Member] | Solid Capacitors | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Accrual Adjustment			100
Europe
Restructuring Cost and Reserve [Line Items]
Workforce reductions and administrative overhead			200
FLORIDA | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges			2,700
FLORIDA | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 900
Granna, Sweden [Member] | Film and Electrolytic | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	700
Restructuring and Related Cost, Incurred Cost	732
Cumulative incurred to date	732
Granna, Sweden [Member] | Film and Electrolytic | Manufacturing and sales office relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	2,000	$ 2,300
Granna, Sweden [Member] | Film and Electrolytic | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	2,018
Cumulative incurred to date	$ 4,313
Customer Relationships
Restructuring Cost and Reserve [Line Items]
Useful life	12 years 2 months 12 days	12 years 3 months 12 days
TOKIN | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 5,000
MnO2 product line headcount reduction | Solid Capacitors | Personnel Reduction Costs
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost		$ 1,600