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

COMMITMENTS AND CONTINGENCIES (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended		3 Months Ended
	Jun. 30, 2013 Drilling Rig Commitments item	Jun. 30, 2013 Drilling Rig Commitments One	Jun. 30, 2013 Drilling Rig Commitments Two	Jun. 30, 2013 Transportation Agreements
COMMITMENTS AND CONTINGENCIES
Amount of increase in the future aggregate obligations under the transportation agreements				$ 25.3
Number of drilling rig commitments	2
Drilling rig commitment term		2 years	3 years
Drilling Rig Commitments
2013	7.0
2014	14.9
2015	6.8
2016	$ 4.4