COMMITMENTS AND CONTINGENCIES (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2013 item
Drilling Rig Commitments
COMMITMENTS AND CONTINGENCIES
Number of drilling rig commitments	2
Drilling Rig Commitments
2013	$ 3.4
2014	14.9
2015	6.8
2016	4.4
Drilling Rig Commitments One
COMMITMENTS AND CONTINGENCIES
Drilling rig commitment term	2 years
Drilling Rig Commitments Two
COMMITMENTS AND CONTINGENCIES
Drilling rig commitment term	3 years
Transportation Agreements
COMMITMENTS AND CONTINGENCIES
Amount of increase in the future aggregate obligations under the transportation commitments	$ 49.4

Represents the term of the drilling rig commitment of the entity.

No definition available.

Name:	cog_DrillingRigCommitmentTerm
Namespace Prefix:	cog_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the increase (decrease) in aggregate future obligations for the transportation agreements during the period.

No definition available.

Name:	cog_IncreaseDecreaseInAggregateFutureTransportationAgreementObligation
Namespace Prefix:	cog_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the number of drilling rig commitments entered into by the entity.

No definition available.

Name:	cog_NumberOfDrillingRigCommitments
Namespace Prefix:	cog_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Amount of contractual obligation maturing in the fourth fiscal year following the latest fiscal year.

No definition available.

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

Amount of contractual obligation maturing in the second fiscal year following the latest fiscal year.

No definition available.

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

Amount of contractual obligation maturing in the third fiscal year following the latest fiscal year.

No definition available.

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

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

Amount of contractual obligation maturing in the remainder of the fiscal year following the latest fiscal year ended.

No definition available.

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

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