The amount of total contract value.

No definition available.

Name:	tcp_ContractValue
Namespace Prefix:	tcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Development costs incurred by related party that the entity is obligated to reimburse, including capitalized costs and costs charged to expense, in oil and gas activities.

+ References

No definition available.

+ Details

Name:	tcp_CostsIncurredDevelopmentCostsReimbursableToRelatedParty
Namespace Prefix:	tcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The period over which the expansion project is designed to be phased in.

+ References

No definition available.

+ Details

Name:	tcp_ExpansionProjectPhaseInPeriod
Namespace Prefix:	tcp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The contractual term of long term transportation capacity.

+ References

No definition available.

+ Details

Name:	tcp_LongTermTransportationCapacityContractTerm
Namespace Prefix:	tcp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Related Party, Contract Capacity

+ References

No definition available.

+ Details

Name:	tcp_RelatedPartyContractCapacity
Namespace Prefix:	tcp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Related Party, Contract Value Terminated

+ References

No definition available.

+ Details

Name:	tcp_RelatedPartyContractValueTerminated
Namespace Prefix:	tcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of receivables arising from transactions with related parties due within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
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-Paragraph 1
-Subparagraph (SX 210.5-02.3(a)(2))
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-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864

+ Details

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

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
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-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

+ Details

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

+ Details

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

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_GeneralPartnerMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=tcp_ReimbursementOfCostsOfServicesProvidedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=tcp_GreatLakesGasTransmissionLimitedPartnershipMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=tcp_TransCanadaCorporationAndSubsidiariesExcludingGeneralPartnerSubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=tcp_AnrPipelineCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=tcp_TransportationContractsRelatedPartyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
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- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_SalesRevenueNetMember
Namespace Prefix:
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Balance Type:
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- Details

Name:	dei_LegalEntityAxis=tcp_PortlandNaturalGasTransmissionSystemMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=tcp_PortlandXpressExpansionProjectPhaseThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_AffiliatedEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix:
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RELATED PARTY TRANSACTIONS - Narrative (Details) MMBTU / d in Thousands, $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($) MMBTU / d	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Nov. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
General Partner \| Reimbursement of costs of services provided
Related Party Transaction [Line Items]
Costs charged	$ 1.0		$ 1.0	$ 2.0	$ 2.0
Great Lakes \| TC Energy
Related Party Transaction [Line Items]
Amount included in receivables from related party	$ 13.0			$ 13.0				$ 19.0
Great Lakes \| ANR Pipeline Company \| Transportation contracts
Related Party Transaction [Line Items]
Contract value		$ 182.0				$ 1,300.0
Contract term		20 years				15 years
Contract value terminated		$ 1,100.0
Related Party, Contract Capacity \| MMBTU / d		168
Great Lakes \| Customer concentration risk \| Total net revenues \| TC Energy \| Transportation contracts
Related Party Transaction [Line Items]
Percent of total revenues	75.00%		73.00%	74.00%	73.00%
PNGTS \| TC Energy \| Portland XPress expansion project (PXP), Phase III
Related Party Transaction [Line Items]
Development costs, reimbursable	$ 3.8			$ 3.8
PNGTS \| Affiliates \| Portland XPress expansion project (PXP), Phase III
Related Party Transaction [Line Items]
Phase in period				3 years
Forecast \| PNGTS \| TC Energy \| Portland XPress expansion project (PXP), Phase III
Related Party Transaction [Line Items]
Development costs, reimbursable							$ 9.1