Organization and Significant Accounting Policies - Options (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Fair Value Measurement
Money markets	$ 2,055	$ 738
Debt, Long-term and Short-term, Combined Amount	(388,211)	(387,833)
Forward Option Net Asset Liability Fair Value	(9,900)	(20,600)
Fair Value Net Forward Option Asset Liability Measured on Recurring Basis Unobservable Input Reconciliation [Roll Forward]
Change in value of TOKIN options	10,700	(26,300)	$ 2,100
Put Option \| NECTOKIN
Fair Value Measurement
Forward Option Net Asset Liability Fair Value	(9,900)	(20,600)
Recurring
Fair Value Measurement
Money markets	2,055	738
Debt, Long-term and Short-term, Combined Amount	(385,251)	(284,261)
Recurring \| Level 1
Fair Value Measurement
Money markets	2,055	738
Debt, Long-term and Short-term, Combined Amount	(353,000)	(254,713)
Recurring \| Level 1 \| Put Option \| NECTOKIN
Fair Value Measurement
Forward Option Net Asset Liability Fair Value	0	0
Recurring \| Level 2
Fair Value Measurement
Money markets	0	0
Debt, Long-term and Short-term, Combined Amount	(32,251)	(29,548)
Recurring \| Level 2 \| Put Option \| NECTOKIN
Fair Value Measurement
Forward Option Net Asset Liability Fair Value	0	0
Recurring \| Level 3
Fair Value Measurement
Money markets	0	0
Debt, Long-term and Short-term, Combined Amount	0	0
Recurring \| Level 3 \| Put Option \| NECTOKIN
Fair Value Net Forward Option Asset Liability Measured on Recurring Basis Unobservable Input Reconciliation [Roll Forward]
Change in value of TOKIN options	10,700	(26,300)	2,100
Other Noncurrent Assets [Member] \| Recurring \| Level 3 \| Put Option \| NECTOKIN
Fair Value Measurement
Forward Option Net Asset Liability Fair Value	$ (9,900)	$ (20,600)	$ 5,700

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Fair value of the forward option net asset (liability).

+ References

No definition available.

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- Definition

Represents the aggregate of total long-term debt, including current maturities and short-term debt.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14172-108612

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- Definition

Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash Equivalents
-URI http://asc.fasb.org/extlink&oid=6507016

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