Components of the Acquisition Price [Abstract]

No definition available.

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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.

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No definition available.

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The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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- Definition

The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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- Definition

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

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- Definition

The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

+ References

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- Definition

In a business combination in which the amount of net identifiable assets acquired and liabilities assumed exceeds the aggregate consideration transferred or to be transferred (as defined), this element represents the amount of gain recognized by the entity.

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- Definition

In a business combination achieved in stages, this element represents the amount of net gain (loss) recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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- Definition

This element represents the weighted average total number of shares issued throughout the period including the first (beginning balance outstanding) and last (ending balance outstanding) day of the period before considering any reductions (for instance, shares held in treasury) to arrive at the weighted average number of shares outstanding. Weighted average relates to the portion of time within a reporting period that common shares have been issued and outstanding to the total time in that period. Such concept is used in determining the weighted average number of shares outstanding for purposes of calculating earnings per share (basic).

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Acquisitions Acquisitions - Pro Forma Results (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended
	Apr. 19, 2017	Apr. 19, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Mar. 12, 2012
Components of the Acquisition Price [Abstract]
Pro forma revenues			$ 1,217,400	$ 1,061,230
Pro forma net income (loss) from continuing operations available to common stockholders			$ 52,377	$ 226,918
Pro forma earnings per common share - basic (in dollars per share)			$ 0.99	$ 4.87
Pro forma earnings per common share - diluted (in dollars per share)			$ 0.89	$ 4.10
Pro forma common shares - basic (in shares)						52,798	46,552	46,004
Pro forma common shares - diluted (in shares)			58,640		46,004		55,389
Business Acquisition [Line Items]
Equity income (loss) from equity method investments		$ 76,192				$ 76,192	$ 41,643	$ (16,406)
Business combination bargain purchase, gain recognized						130,880	0	0
TOKIN
Business Acquisition [Line Items]
Remeasurement gain (loss)			$ 66,700		$ 68,700
Business combination bargain purchase, gain recognized	$ 62,159		$ 60,300
NEC TOKIN Corporation
Business Acquisition [Line Items]
Equity income (loss) from equity method investments						$ 75,177	$ 41,643	$ (16,406)
NEC TOKIN Corporation \| Stock Purchase Agreement \| KEMET Electronics Corporation
Business Acquisition [Line Items]
Ownership percentage			34.00%		34.00%	34.00%	34.00%	34.00%	34.00%
TOKIN
Business Acquisition [Line Items]
Equity income (loss) from equity method investments		$ 75,200	$ 123,400