Impairment Charges Impairment Charges - Narrative (Details) - USD ($)	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Property, Plant and Equipment [Line Items]
Write down of long-lived assets	$ 10,279,000	$ 0	$ 0
Asset Impairment Charges	$ 10,279,000	0	0
Document Period End Date	Mar. 31, 2017
Solid Capacitors
Property, Plant and Equipment [Line Items]
Write down of long-lived assets	$ 2,076,000
Asset Impairment Charges		0	0
Film and Electrolytic
Property, Plant and Equipment [Line Items]
Asset Impairment Charges	8,200,000	$ 0	$ 0
TENNESSEE | Film and Electrolytic
Property, Plant and Equipment [Line Items]
Asset Impairment Charges	4,100,000
Impairment of Long-Lived Assets to be Disposed of	3,000,000
Impairment of Intangible Assets (Excluding Goodwill)	1,100,000
Italy | Film and Electrolytic
Property, Plant and Equipment [Line Items]
Asset Impairment Charges	4,100,000
Facility Closing [Member] | Solid Capacitors
Property, Plant and Equipment [Line Items]
Restructuring and Related Cost, Expected Cost Remaining	700,000
Facility Closing [Member] | Mexico | Solid Capacitors
Property, Plant and Equipment [Line Items]
Restructuring and Related Cost, Cost Incurred to Date	$ 600,000
Basic [Member] | Solid Capacitors
Property, Plant and Equipment [Line Items]
Impairment Effect on Earnings Per Share, Pretax	$ 0.04
Basic [Member] | Film and Electrolytic
Property, Plant and Equipment [Line Items]
Impairment Effect on Earnings Per Share, Pretax	0.18
Diluted [Member] | Solid Capacitors
Property, Plant and Equipment [Line Items]
Impairment Effect on Earnings Per Share, Pretax	0.04
Diluted [Member] | Film and Electrolytic
Property, Plant and Equipment [Line Items]
Impairment Effect on Earnings Per Share, Pretax	$ 0.15