Goodwill and Intangible Assets - Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Goodwill [Line Items]
Goodwill	$ (40,294)	$ (40,294)
Solid Capacitors
Goodwill [Line Items]
Goodwill	35,584	35,584
Accumulated impairment losses	0	0
Goodwill	(35,584)	(35,584)
Film and Electrolytic
Goodwill [Line Items]
Goodwill	1,092	1,092
Accumulated impairment losses	(1,092)	(1,092)
Goodwill	0	0
Corporate
Goodwill [Line Items]
Goodwill	4,710	4,710
Accumulated impairment losses	0
Goodwill	(4,710)
Goodwill, Acquired During Period	$ 0	$ 4,710

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=64834752&loc=SL49117168-202975

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount before accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of accumulated impairment loss for an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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