Business Combination, Indemnity Asset

No definition available.

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Data Type:	xbrli:monetaryItemType
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- Definition

Business Combination, Put Option Liability

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Equity Method Investment, Indemnity Asset

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of liability recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6911338&loc=d3e6819-128478

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

For indemnification assets recognized in connection with a business combination, this element represents an estimate of the low-end of the potential range (undiscounted) of the indemnification benefit which may be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

+ References

No definition available.

+ Details

Name:	us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of financial instrument classified as derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19279-110258

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Foreign exchange rate used to translate amounts denominated in functional currency to reporting currency.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6897108&loc=SL6897125-166521

+ Details

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- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

+ Details

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Period Type:	duration

- Details

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- Details

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- Details

Name:	dei_LegalEntityAxis=kem_TOKINMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=kem_TOKINMember
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- Details

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- Details

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- Details

Name:	kem_InitialConsiderationAxis=kem_ExcesscashMember
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=us-gaap_CashDistributionMember
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- Details

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- Details

Name:	us-gaap_BusinessAcquisitionAxis=us-gaap_OtherAssetsMember
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- Details

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Acquisitions Acquisitions - Components of the Acquisition Price (Details) $ in Thousands, ¥ in Billions	Apr. 19, 2017 USD ($) Rate	Apr. 19, 2017 JPY (¥)	Dec. 31, 2017 USD ($) Rate	Dec. 31, 2017 JPY (¥) Rate	Sep. 30, 2017 Rate	Apr. 19, 2017 JPY (¥) Rate	Apr. 14, 2017 USD ($)	Apr. 14, 2017 JPY (¥)	Mar. 31, 2017 Rate
Business Acquisition [Line Items]
Exchange rate \| Rate	10900.70%		11257.40%	11257.40%	11250.20%	10900.70%			11182.30%
Indemnity asset for legal investigation	$ 8,500
Equity Method Investments \| Stockholders Agreement
Business Acquisition [Line Items]
Indemnification assets, low range of outcomes			$ 25,000
TOKIN
Business Acquisition [Line Items]
Net consideration transferred	150,358
Purchase price			$ 10,100	¥ 1.1		¥ 10.2	$ 431,000	¥ 48.2
TOKIN \| KEC
Business Acquisition [Line Items]
Upfront cash consideration	$ 148,600	¥ 16.2
Interest acquired	66.00%					66.00%
TOKIN \| KEC \| Cash Distribution
Business Acquisition [Line Items]
Upfront cash consideration	$ 55,000	6.0
TOKIN \| KEC \| Excess cash
Business Acquisition [Line Items]
Upfront cash consideration	93,600	¥ 10.2
Cash Distribution \| TOKIN
Business Acquisition [Line Items]
Upfront cash consideration	148,614
Acquisition-related Costs \| TOKIN
Business Acquisition [Line Items]
Acquisition payable	3,144
Other Assets \| TOKIN
Business Acquisition [Line Items]
Indemnity asset	8,500
Put Option \| TOKIN
Business Acquisition [Line Items]
Less: Put option	(9,900)
Net derivative asset (liability)	$ (9,900)