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

Represents the capitalized exploratory well costs that were subsequently expensed in the same period.

No definition available.

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

The amount of capitalized exploratory well costs that have been capitalized for a period greater than or equal to one year but less than three years after the completion of drilling at balance sheet date.

No definition available.

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

The amount of capitalized exploratory well costs that have been capitalized for a period greater than or equal to three years but less than five years after completion of drilling at balance sheet date.

No definition available.

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

Represents the period of negotiation and consultation of notice of dispute issued to Ministry of Energy that can be extended if mutually agreed upon.

No definition available.

Name:	kos_PeriodOfNegotiationAndConsultationOfNoticeOfDisputeGivenToMinistryOfEnergy
Namespace Prefix:	kos_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the portion of wells which are designed for water and gas injection to support field recoveries

No definition available.

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

Represents the portion of wells which are designed as producers.

No definition available.

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

Represents the period taken, after a declaration of commerciality, if any, in which a plan of development would be prepared and submitted to Ministry of Energy.

No definition available.

Name:	kos_SubmissionOfPlanOfDevelopmentToMinistryOfEnergyPeriod
Namespace Prefix:	kos_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

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

Additions to capitalized exploratory well costs that were added during the reporting period pending the determination of proved reserves.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 1B

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS19-1

-Paragraph 10

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

The amount of capitalized exploratory well costs that is pending the determination of proved reserves. This does not include amounts that were capitalized and subsequently expensed in the same annual period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 1B

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS19-1

-Paragraph 10

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

The amount of exploratory well costs that have been capitalized for a period of one year or less after the completion of drilling.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS19-1

-Paragraph 10

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 16

-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61939-109447

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

The number of productive developmental wells drilled in the geographic area. A productive well is a well that is not a dry well. The number of wells drilled refers to the number of wells (holes) completed at any time during the fiscal years, regardless when drilling was initiated.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Industry Guide

-Number 2

-Paragraph 6

-Subparagraph A

Name:	us-gaap_DevelopmentWellsDrilledNetProductive
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

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

The number of productive exploratory wells drilled in the geographic area. A productive well is a well that is not a dry well. The number of wells drilled refers to the number of wells (holes) completed at any time during the fiscal years, regardless when drilling was initiated.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Industry Guide

-Number 2

-Paragraph 6

-Subparagraph A

Name:	us-gaap_ExploratoryWellsDrilledNetProductive
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

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

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

The number of projects for which exploratory well costs have been capitalized for a period of greater than one year after the completion of drilling.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 1B

-Subparagraph b

-URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS19-1

-Paragraph 10

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.