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

Represents the number of rig slots taken by the third party.

No definition available.

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

Represents the period the entity has the option to extend the drilling rig contract.

No definition available.

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

Represents the period of offshore drilling rig contract entered into by the entity.

No definition available.

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

Represents the initial rig rate per day under an offshore drilling rig contract entered into by the entity.

No definition available.

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

Represents the rate per day under an offshore drilling contract entered into by the entity.

No definition available.

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

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

Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 10

-Section 55

-Paragraph 40

-Subparagraph (Note 3)

-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717

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

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

Amount of required minimum rental payments maturing in the fifth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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

Amount of required minimum rental payments maturing in the forth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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

Amount of required minimum rental payments maturing in the third fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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

Amount of required minimum rental payments maturing in the second fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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

Amount of required minimum rental payments maturing in the remainder of the fiscal year following the latest fiscal year ended for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year.

No definition available.

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

Name:	kos_OperatingLeasesAxis=kos_AtwoodAchieverDrillingRigContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: