Represents the available line of credit.

No definition available.

Name:	cog_AvailableLineOfCredit
Namespace Prefix:	cog_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt Instrument, Covenant, Annual Coverage Ratio, Minimum

+ References

No definition available.

+ Details

Name:	cog_DebtInstrumentCovenantAnnualCoverageRatioMinimum
Namespace Prefix:	cog_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Covenant, Asset Coverage Ratio, Minimum

+ References

No definition available.

+ Details

Name:	cog_DebtInstrumentCovenantAssetCoverageRatioMinimum
Namespace Prefix:	cog_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the ratio of current assets to current liabilities.

+ References

No definition available.

+ Details

Name:	cog_DebtInstrumentCovenantCurrentRatioMinimum
Namespace Prefix:	cog_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of trailing quarters used to calculate the annual coverage ratio.

+ References

No definition available.

+ Details

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

- Definition

Represents the percentage of the entity's total indebtedness to its borrowing base under the credit facility under the fourth level.

+ References

No definition available.

+ Details

Name:	cog_LineOfCreditFacilityBasisSpreadIncreaseTotalIndebtednessPercentageOfBorrowingBaseLevelFour
Namespace Prefix:	cog_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the percentage of the entity's total indebtedness to its borrowing base under the credit facility under the first level.

+ References

No definition available.

+ Details

Name:	cog_LineOfCreditFacilityBasisSpreadIncreaseTotalIndebtednessPercentageOfBorrowingBaseLevelOne
Namespace Prefix:	cog_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the percentage of the entity's total indebtedness to its borrowing base under the credit facility under the third level.

+ References

No definition available.

+ Details

Name:	cog_LineOfCreditFacilityBasisSpreadIncreaseTotalIndebtednessPercentageOfBorrowingBaseLevelThree
Namespace Prefix:	cog_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the percentage of the entity's total indebtedness to its borrowing base under the credit facility under the second level.

+ References

No definition available.

+ Details

Name:	cog_LineOfCreditFacilityBasisSpreadIncreaseTotalIndebtednessPercentageOfBorrowingBaseLevelTwo
Namespace Prefix:	cog_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the period over which the entity has to reduce its outstanding borrowings in the event that the adjusted credit line available is less than outstanding borrowings.

+ References

No definition available.

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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

- Details

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

- Definition

The effective interest rate during the reporting period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 7

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20, 22

-Article 5

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

- Definition

Weighted average interest rate of long-term debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_LongtermDebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt and Credit Agreements (Details 3) (USD $)	12 Months Ended
Debt and Credit Agreements (Details 3) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 15, 2014	Apr. 14, 2014
Debt
Debt	$ 1,752,000,000us-gaap_LongTermDebt	$ 1,147,000,000us-gaap_LongTermDebt
Revolving credit facility
Debt
Period to reduce outstanding debt in equal monthly installments to the adjusted credit line available	6 months
Line of credit	1,400,000,000
Borrowing base				3,100,000,000.0	2,300,000,000.0
Number of trailing quarters used to calculate annual coverage ratio	12 months
Annual coverage ratio, minimum	2.8
Asset coverage ratio, minimum	1.75
Current ratio, minimum	1.0
Debt	140,000,000	460,000,000
Availability under the credit facility	$ 1,300,000,000
Weighted-average effective interest rates (as a percent)	2.20%	2.30%	3.00%
Weighted-average interest rate (as a percent)	2.40%	2.00%
Revolving credit facility \| Greater than
Debt
Percentage of the entity's total indebtedness to its borrowing base under the credit facility under the first level	25.00%
Percentage of the entity's total indebtedness to its borrowing base under the credit facility under the second level	50.00%
Percentage of the entity's total indebtedness to its borrowing base under the credit facility under the third level	75.00%
Percentage of the entity's total indebtedness to its borrowing base under the credit facility under the fourth level	90.00%
Commitment fee percentage	0.375%
Revolving credit facility \| Less than or equal to
Debt
Commitment fee percentage	0.50%
Revolving credit facility \| Eurodollar Loans
Debt
Description of variable rate basis	Euro-Dollars (LIBOR)
Revolving credit facility \| ABR Loans
Debt
Description of variable rate basis	Alternate Base Rate (ABR)
Revolving credit facility \| Less than 25 percent \| Eurodollar Loans
Debt
Margin (as a percent)	1.50%
Revolving credit facility \| Less than 25 percent \| ABR Loans
Debt
Margin (as a percent)	0.50%
Revolving credit facility \| Greater than equal to 25 percent but less than 50 percent \| Eurodollar Loans
Debt
Margin (as a percent)	1.75%
Revolving credit facility \| Greater than equal to 25 percent but less than 50 percent \| ABR Loans
Debt
Margin (as a percent)	0.75%
Revolving credit facility \| Greater than equal to 50 percent but less than 75 percent \| Eurodollar Loans
Debt
Margin (as a percent)	2.00%
Revolving credit facility \| Greater than equal to 50 percent but less than 75 percent \| ABR Loans
Debt
Margin (as a percent)	1.00%
Revolving credit facility \| Greater than equal to 75 percent but less than 90 percent \| Eurodollar Loans
Debt
Margin (as a percent)	2.25%
Revolving credit facility \| Greater than equal to 75 percent but less than 90 percent \| ABR Loans
Debt
Margin (as a percent)	1.25%
Revolving credit facility \| Greater than and equal to 90 percent \| Eurodollar Loans
Debt
Margin (as a percent)	2.50%
Revolving credit facility \| Greater than and equal to 90 percent \| ABR Loans
Debt
Margin (as a percent)	1.50%