Goodwill and Other Intangible Assets - Components of Other Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Mar. 31, 2024	Mar. 31, 2024	Jun. 30, 2023
The components of intangible assets
Accumulated amortization	$ (181,798)	$ (181,798)	$ (173,346)
Intangible Assets, Gross (Excluding Goodwill)	$ 266,204	$ 266,204	266,510
Metal Cutting
The components of intangible assets
Business Combination, Reason for Business Combination	$3.6 million	$6.5 million.
Trademarks [Member]
The components of intangible assets
Gross carrying amount, Indefinite	$ 0	$ 0	10,836
Technology-based and other [Member]
The components of intangible assets
Gross carrying amount, finite	31,781	31,781	31,872
Accumulated amortization	(24,354)	(24,354)	(23,838)
Customer-related [Member]
The components of intangible assets
Gross carrying amount, finite	179,759	179,759	179,889
Accumulated amortization	(118,446)	(118,446)	(112,890)
Unpatented technology [Member]
The components of intangible assets
Gross carrying amount, finite	31,504	31,504	31,487
Accumulated amortization	(26,718)	(26,718)	(25,177)
Trademarks [Member]
The components of intangible assets
Gross carrying amount, finite	23,160	23,160	12,426
Accumulated amortization	$ (12,280)	$ (12,280)	$ (11,441)
Minimum [Member] \| Technology-based and other [Member]
The components of intangible assets
Useful life related to technology-based intangible assets	4 years	4 years
Minimum [Member] \| Customer-related [Member]
The components of intangible assets
Useful life related to technology-based intangible assets	10 years	10 years
Minimum [Member] \| Unpatented technology [Member]
The components of intangible assets
Useful life related to technology-based intangible assets	10 years	10 years
Minimum [Member] \| Trademarks [Member]
The components of intangible assets
Useful life related to technology-based intangible assets	5 years	5 years
Maximum [Member] \| Technology-based and other [Member]
The components of intangible assets
Useful life related to technology-based intangible assets	20 years	20 years
Maximum [Member] \| Customer-related [Member]
The components of intangible assets
Useful life related to technology-based intangible assets	21 years	21 years
Maximum [Member] \| Unpatented technology [Member]
The components of intangible assets
Useful life related to technology-based intangible assets	30 years	30 years
Maximum [Member] \| Trademarks [Member]
The components of intangible assets
Useful life related to technology-based intangible assets	20 years	20 years

The components of intangible assets.

No definition available.

Name:	kmt_ComponentsOfIntangibleAssetsAbstract
Namespace Prefix:	kmt_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents a description of the primary reason for the business combination which may consist of general categories such as top-line growth, synergistic benefits, market share, and diversification and the more detailed factors that might apply.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479328/805-10-50-2

+ Details

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

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(16))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482665/350-30-50-2

+ Details

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

- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 928
-SubTopic 340
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483147/928-340-50-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482665/350-30-50-2

+ Details

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

- Definition

Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482665/350-30-50-2

+ Details

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

- Definition

Amount before accumulated amortization of intangible assets, excluding goodwill.

+ References

+ Details

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

- Details

Name:	us-gaap_BusinessAcquisitionAxis=kmt_MetalCuttingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_TrademarksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=kmt_TechnologyBasedAndOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_UnpatentedTechnologyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_TrademarksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: