Represents the percentage of participation interest acquired during the period.

No definition available.

Name:	kos_AcquiredParticipationInterestPercentage
Namespace Prefix:	kos_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the amount of spend on development costs whereby, a third party will pay Kosmos costs

+ References

No definition available.

+ Details

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

- Definition

Represents the amount of spend on exploration and appraisal costs, whereby, a third party will pay Kosmos costs.

+ References

No definition available.

+ Details

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

- Definition

Amount of potential and variable consideration per barrel to be paid by third party.

+ References

No definition available.

+ Details

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

- Definition

Represents the percentage increase in the entity's equity in each contract area.

+ References

No definition available.

+ Details

Name:	kos_EquityIncreaseInEachContractAreaPercentage
Namespace Prefix:	kos_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the maximum gross amount to be incurred per contingent exploration well, whereby, Kosmos will pay all of a third party's cost

+ References

No definition available.

+ Details

Name:	kos_MaximumAmountOfContingentExplorationWellCost
Namespace Prefix:	kos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents number of barrels

+ References

No definition available.

+ Details

Name:	kos_NumberOfBarrels
Namespace Prefix:	kos_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of blocks covered by farm-out agreements.

+ References

No definition available.

+ Details

Name:	kos_NumberOfBlocksCoveredByFarmOutAgreements
Namespace Prefix:	kos_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the participating interest percentage.

+ References

No definition available.

+ Details

Name:	kos_ParticipatingInterestPercentage
Namespace Prefix:	kos_
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

Name:	kos_PropertyPlantAndEquipmentAcquisitionsAndDivestituresLineItems
Namespace Prefix:	kos_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Reduction of oil and gas properties with unproved reserves under the successful effort method.

+ References

No definition available.

+ Details

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

- Definition

Amount of upfront cash paid by third party.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow to dispose of long-lived, physical assets and mineral interests in oil and gas properties used for normal oil and gas operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3179-108585

+ Details

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

- Details

Name:	kos_OilAndGasBlocksAxis=kos_MauritaniaAndSenegalOffshoreBlockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=kos_KosmosBpSenegalLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	kos_OilAndGasBlocksAxis=kos_CayarOffshoreProfondAndSaintLouisOffshoreProfondBlocksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	kos_OilAndGasAgreementAxis=kos_SalesAndPurchaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	kos_OilAndGasAgreementAxis=kos_SalesAndPurchaseAgreementAndFarmOutAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=kos_TimisCorporationLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	kos_OilAndGasAgreementAxis=kos_FarmInAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=kos_BPPlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	kos_OilAndGasAgreementAxis=kos_FarmOutAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	kos_OilAndGasBlocksAxis=kos_BlockC6BlockC8BlockC12AndBlockC13MauritaniaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Acquisitions and Divestitures (Details) bbl in Billions	1 Months Ended			3 Months Ended
Acquisitions and Divestitures (Details) bbl in Billions	Feb. 28, 2017	Jan. 31, 2017 item	Dec. 31, 2016 USD ($) bbl	Mar. 31, 2017 USD ($)
Acquisitions and Divestitures
Proceeds on sale of assets				$ 203,919,000
Mauritania And Senegal Offshore Block \| Maximum
Acquisitions and Divestitures
Spending by third party for exploration and appraisal costs				$ 221,000,000
Kosmos BP Senegal Limited \| Cayar Offshore Profond And Saint Louis Offshore Profond Blocks
Acquisitions and Divestitures
Participating interests (as a percent)				60.00%
Sales and purchase agreement \| Kosmos BP Senegal Limited \| Cayar Offshore Profond And Saint Louis Offshore Profond Blocks
Acquisitions and Divestitures
Participating interests (as a percent)	60.00%		65.00%
Percentage increase in equity in each contract area			5.00%
Sales and purchase agreement and farm-out agreements \| Mauritania And Senegal Offshore Block
Acquisitions and Divestitures
Reduction in unproved property				$ 221,900,000
Timis Corporation Limited \| Cayar Offshore Profond And Saint Louis Offshore Profond Blocks
Acquisitions and Divestitures
Participating interests (as a percent)				30.00%
Timis Corporation Limited \| Farm-in agreement \| Cayar Offshore Profond And Saint Louis Offshore Profond Blocks
Acquisitions and Divestitures
Maximum cost per contingent exploration well			$ 120,000,000
BP \| Farm-out agreements \| Block C6 Block C8 Block C12 and Block C13 Mauritania
Acquisitions and Divestitures
Number of blocks covered by farm-out agreements \| item		4
Participation interest acquired (as a percent)		62.00%
BP \| Farm-out agreements \| Mauritania And Senegal Offshore Block
Acquisitions and Divestitures
Amount of potential and variable consideration per barrel			$ 2
BP \| Farm-out agreements \| Mauritania And Senegal Offshore Block \| Maximum
Acquisitions and Divestitures
Number of barrels \| bbl			1.0
BP \| Sales and purchase agreement \| Kosmos BP Senegal Limited
Acquisitions and Divestitures
Participation interest acquired (as a percent)	49.99%
BP \| Sales and purchase agreement and farm-out agreements \| Mauritania And Senegal Offshore Block
Acquisitions and Divestitures
Upfront amount of cash received				$ 162,000,000
Spending by third party for exploration and appraisal costs			$ 221,000,000
Spending by third party for Kosmos' development costs			$ 533,000,000