Disposal Of Participating Interest, Percentage

No definition available.

Name:	kos_DisposalOfParticipatingInterestPercentage
Namespace Prefix:	kos_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Participating Interest In Oil And Gas Exploration, Percentage

+ References

No definition available.

+ Details

Name:	kos_ParticipatingInterestInOilAndGasExplorationPercentage
Namespace Prefix:	kos_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Proceeds From Divestitures In Participating Interest

+ References

No definition available.

+ Details

Name:	kos_ProceedsFromDivestituresInParticipatingInterest
Namespace Prefix:	kos_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Share Sale And Purchase Agreement, Consideration Transferred

+ References

No definition available.

+ Details

Name:	kos_ShareSaleAndPurchaseAgreementConsiderationTransferred
Namespace Prefix:	kos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Share Sale And Purchase Agreement, Contingent Consideration

+ References

No definition available.

+ Details

Name:	kos_ShareSaleAndPurchaseAgreementContingentConsideration
Namespace Prefix:	kos_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Share Sale And Purchase Agreement, Participating Interest

+ References

No definition available.

+ Details

Name:	kos_ShareSaleAndPurchaseAgreementParticipatingInterest
Namespace Prefix:	kos_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Share Sale And Purchase Agreement, Purchase Price Adjustments

+ References

No definition available.

+ Details

Name:	kos_ShareSaleAndPurchaseAgreementPurchasePriceAdjustments
Namespace Prefix:	kos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 805
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479581/805-30-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 805
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479581/805-30-50-1

+ Details

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

- Definition

Amount of gain (loss) on sale or disposal of oil and gas property or timber property.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482130/360-10-45-5

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482099/360-10-50-3

+ Details

Name:	us-gaap_GainLossOnSaleOfProperty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-12

+ Details

Name:	us-gaap_ProceedsFromDivestitureOfBusinesses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=kos_KeathleyCanyonBlocksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	kos_ShareSaleAndPurchaseAgreementContingentConsiderationAxis=kos_ShareSaleAndPurchaseAgreementContingentConsiderationTrancheOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	kos_ShareSaleAndPurchaseAgreementContingentConsiderationAxis=kos_ShareSaleAndPurchaseAgreementContingentConsiderationTrancheTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	kos_ShareSaleAndPurchaseAgreementContingentConsiderationAxis=kos_ShareSaleAndPurchaseAgreementContingentConsiderationTrancheFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	kos_ShareSaleAndPurchaseAgreementContingentConsiderationAxis=kos_ShareSaleAndPurchaseAgreementContingentConsiderationTrancheThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Acquisitions and Divestitures - Narrative (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 24, 2026	Jul. 31, 2026	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Business Combination, Consideration Transferred, Equity Interest [Line Items]
Share sale and purchase agreement, participating interest	40.40%
Share sale and purchase agreement, cash consideration	$ 127,000
Share sale and purchase agreement, initial purchase price	180,000
Share sale and purchase agreement, purchase price adjustments	53,000
Share sale and purchase agreement, future contingent consideration	39,500
Gain (loss) on sale of assets			$ (339)	$ 0	$ 9,082	$ 600
Proceeds from divestitures in participating interest		$ 6,900
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Business Combination, Consideration Transferred, Equity Interest [Line Items]
Gain (loss) on sale of assets					$ 9,400
Keathley Canyon Blocks
Business Combination, Consideration Transferred, Equity Interest [Line Items]
Disposal of participating interest, percentage		16.66%
Participating interest in oil and gas exploration, percentage		33.34%
Share Sale And Purchase Agreement, Contingent Consideration, Tranche One
Business Combination, Consideration Transferred, Equity Interest [Line Items]
Share sale and purchase agreement, future contingent consideration	12,500
Share Sale And Purchase Agreement, Contingent Consideration, Tranche Two
Business Combination, Consideration Transferred, Equity Interest [Line Items]
Share sale and purchase agreement, future contingent consideration	9,000
Share Sale And Purchase Agreement, Contingent Consideration, Tranche Four
Business Combination, Consideration Transferred, Equity Interest [Line Items]
Share sale and purchase agreement, future contingent consideration	9,000
Share Sale And Purchase Agreement, Contingent Consideration, Tranche Three
Business Combination, Consideration Transferred, Equity Interest [Line Items]
Share sale and purchase agreement, future contingent consideration	$ 9,000