Represents the period for of drilling and completion carry from the closing of the transaction.

No definition available.

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

- Definition

Represents the amount certain to be funded for future drilling and completion costs by Osaka Gas Co., Ltd., associated with leaseholds.

+ References

No definition available.

+ Details

Name:	cog_FutureDrillingAndCompletionCostsToBeFundedByThirdParty
Namespace Prefix:	cog_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the percentage of non-operated working interest sold by the entity to a third party.

+ References

No definition available.

+ Details

Name:	cog_NonOperatedWorkingInterest
Namespace Prefix:	cog_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Third party reimbursement percentage of drilling costs, including completion costs.

+ References

No definition available.

+ Details

Name:	cog_ReimbursementPercentageOfCompletionAndDrillingCosts
Namespace Prefix:	cog_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainLossOnSaleOfPropertyPlantEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from the sale of property, plant and equipment (capital expenditures), software, and other intangible assets.

+ 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=31042434&loc=d3e3179-108585

+ Details

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

- Definition

The value of all consideration given or received by the Entity in the significant acquisition or disposal.

+ References

No definition available.

+ Details

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

- Details

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

PROPERTIES AND EQUIPMENT, NET (Details 3) (USD $)	3 Months Ended		9 Months Ended		1 Months Ended
PROPERTIES AND EQUIPMENT, NET (Details 3) (USD $)	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2012 Pearsall shale	Oct. 31, 2013 Oklahoma and Texas panhandles oil and gas properties Subsequent event	Oct. 31, 2013 West Texas oil and gas properties Subsequent event
Significant Acquisitions and Disposals
Non-operated working interest (as a percent)					35.00%
Total consideration received from the sale of properties					$ 251,000,000	$ 160,000,000	$ 28,000,000
Proceeds from sale of oil and gas properties					125,000,000
Gain on sale of assets	4,421,000	(126,000)	4,601,000	67,042,000	67,000,000
Percentage of fund for the Company's share of future drilling and completion costs					85.00%
Future drilling and completion costs to be funded by third party					$ 126,000,000
Drilling and completion carry					2 years