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v3.20.4

Derivative Instruments and Hedging Activities, Pro Forma Impact - Offsetting Collateral (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Derivative Asset [Abstract] |  |
Gross collateral | $ 29.8 | $ (4.9)
Counterparties with Offsetting Positions or Collateral [Member] |  |
Derivative Asset [Abstract] |  |
Gross collateral | 29.8 | (4.9)
Current Assets from Risk Management Activities [Member] |  |
Derivative Asset [Abstract] |  |
Gross collateral | 29.8 | (4.9)
Current Assets from Risk Management Activities [Member] | Counterparties with Offsetting Positions or Collateral [Member] |  |
Derivative Asset [Abstract] |  |
Gross collateral | $ 29.8 | $ (4.9)

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- Definition Derivative collateral obligation (right) to return (reclaim) securities. + References No definition available. + Details
Name: | trgp_DerivativeCollateralObligationRightToReturnReclaimSecurities
Namespace Prefix: | trgp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_DerivativeAssetsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_CounterpartyNameAxis=trgp_CounterpartiesWithOffsettingPositionsOrCollateralMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_OtherCurrentAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |