Pension and Other Post-retirement Benefit Plans - Phantom (Details) - Other Benefits	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Health Care Cost Trend Rate on Covered Charges	7.00%	7.00%
Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Ultimate Health Care Cost Trend Rate	5.00%	5.00%
Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Health Care Cost Trend Rate on Covered Charges	7.00%	7.50%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	5.00%	5.00%

Represents the health care cost trend rate on covered charges used as assumptions for calculating benefit obligation.

No definition available.

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Namespace Prefix:	kem_
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Period Type:	instant

- Definition

Represents the ultimate health care cost trend on covered charges used as assumptions for calculating benefit obligation.

+ References

No definition available.

+ Details

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Namespace Prefix:	kem_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the health care cost trend rate on covered charges used as assumptions for calculating net periodic benefit cost.

+ References

No definition available.

+ Details

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Namespace Prefix:	kem_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- 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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Ultimate trend rate for health care cost for defined benefit postretirement plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (l)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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Namespace Prefix:
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