Derivative Instruments and Hedging Activities - Outstanding Commodity Derivatives (Details) MMBbls in Millions, Bcf in Millions	9 Months Ended
Sep. 30, 2017 $ / MMBbls $ / bbl $ / Mcf $ / Bcf MMBbls Bcf
Natural Gas Swap With Contract Period of October 2017 to December 2017
Derivative [Line Items]
Volume (in Bcf for gas and mmbbls for oil) \| Bcf	8.9
Swaps Weighted Average (in usd per Mcf or usd per bbl)	3.12
Natural Gas Swap With Contract Period of October 2017 to December 2017
Derivative [Line Items]
Volume (in Bcf for gas and mmbbls for oil) \| Bcf	4.5
Swaps Weighted Average (in usd per Mcf or usd per bbl)	3.46
Natural Gas Collar With Contract Period of October 2017 to December 2017
Derivative [Line Items]
Volume (in Bcf for gas and mmbbls for oil) \| Bcf	8.9
Natural Gas Collar With Contract Period of October 2017 to December 2017 \| Minimum
Derivative [Line Items]
Collar Ceiling Price (in usd per Mcf or usd per bbl) \| $ / Bcf	3.42
Natural Gas Collar With Contract Period of October 2017 to December 2017 \| Maximum
Derivative [Line Items]
Collar Ceiling Price (in usd per Mcf or usd per bbl) \| $ / Bcf	3.45
Natural Gas Collar With Contract Period of October 2017 to December 2017 \| Weighted Average
Derivative [Line Items]
Collar Floor Price (in usd per Mcf or usd per bbl)	3.09
Collar Ceiling Price (in usd per Mcf or usd per bbl)	3.43
Natural Gas Basis Swap With Contract Period of January 2018 to December 2019
Derivative [Line Items]
Volume (in Bcf for gas and mmbbls for oil) \| Bcf	21.3
Swaps Weighted Average (in usd per Mcf or usd per bbl)	0.42
Crude Oil Collar With Contract Period Of October 2017 to December 2017
Derivative [Line Items]
Volume (in Bcf for gas and mmbbls for oil) \| MMBbls	0.5
Crude Oil Collar With Contract Period Of October 2017 to December 2017 \| Minimum
Derivative [Line Items]
Collar Ceiling Price (in usd per Mcf or usd per bbl) \| $ / MMBbls	56.25
Crude Oil Collar With Contract Period Of October 2017 to December 2017 \| Maximum
Derivative [Line Items]
Collar Ceiling Price (in usd per Mcf or usd per bbl) \| $ / MMBbls	56.50
Crude Oil Collar With Contract Period Of October 2017 to December 2017 \| Weighted Average
Derivative [Line Items]
Collar Floor Price (in usd per Mcf or usd per bbl) \| $ / bbl	50.00
Collar Ceiling Price (in usd per Mcf or usd per bbl) \| $ / bbl	56.39

- Definition

The cap rate on a price risk derivative such as a cap or collar. A payment or receipt is triggered if the market rate exceeds the cap rate on the contract.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeCapPrice
Namespace Prefix:	us-gaap_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	instant

- Definition

Floor rate on a price risk derivative such as a floor or a collar. A payment or receipt is triggered if the market rate falls below the floor rate on the contract.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeFloorPrice
Namespace Prefix:	us-gaap_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountVolume
Namespace Prefix:	us-gaap_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	duration

- Definition

Average fixed price related to the group of price risk swap derivatives.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeSwapTypeAverageFixedPrice
Namespace Prefix:	us-gaap_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cog_NaturalGasSwapWithContractPeriodofOctober2017toDecember2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cog_NaturalGasSwap1WithContractPeriodofOctober2017toDecember2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cog_NaturalGasCollarWithContractPeriodofOctober2017toDecember2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cog_NaturalGasBasisSwapWithContractPeriodofJanuary2018toDecember2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cog_CrudeOilCollarWithContractPeriodOfOctober2017toDecember2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: