Amount of issue refund amongst recourse rate customers during the period of an entity.

No definition available.

Name:	tcp_AmountOfIssueRefundAmongstRecourseRateCustomers
Namespace Prefix:	tcp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of pipelines estimated return on equity

+ References

No definition available.

+ Details

Name:	tcp_EstimatedReturnOnEquity
Namespace Prefix:	tcp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of maximum transportation interim rate increase (decrease) allowed while waiting final decision of regulatory agency.

+ References

No definition available.

+ Details

Name:	tcp_MaximumTransportationInterimRateIncreaseDecreasePercentage
Namespace Prefix:	tcp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of maximum transportation requested rate increase (decrease) with regulatory agency.

+ References

No definition available.

+ Details

Name:	tcp_MaximumTransportationRequestedRateIncreaseDecreasePercentage
Namespace Prefix:	tcp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of reduce recourse rates in cost of service shown in FERC from during the period.

+ References

No definition available.

+ Details

Name:	tcp_PercentOfReduceRecourseRatesInCostOfServicePerUnit
Namespace Prefix:	tcp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percent of decrease in per unit of reservation rates in 2020 agreed upon of last settlement.

+ References

No definition available.

+ Details

Name:	tcp_PercentOfReductionInReservationRatesIn2020OfLastSettlementPerUnit
Namespace Prefix:	tcp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of fair value of investment exceeding its carrying value.

+ References

No definition available.

+ Details

Name:	tcp_PercentageOfFairValueOfInvestmentExceedingCarryingValue
Namespace Prefix:	tcp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year of provision for revenue sharing during the period.

+ References

No definition available.

+ Details

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

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

+ Details

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

- References

No definition available.

+ Details

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

- Details

Name:	us-gaap_RegulatoryAgencyAxis=tcp_FederalEnergyRegulatoryCommissionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=tcp_TuscaroraGasTransmissionCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

REGULATORY (Details) - USD ($) $ in Millions			9 Months Ended	12 Months Ended
REGULATORY (Details) - USD ($) $ in Millions	Oct. 16, 2018	Oct. 11, 2018	Sep. 30, 2018	Dec. 31, 2017
REGULATORY
Goodwill			$ 130	$ 130
Provision for revenue sharing			9
FERC \| Maximum
REGULATORY
Estimated ROE				12.00%
Tuscarora Gas Transmission Company \| FERC
REGULATORY
Goodwill			82	$ 82
GTN \| FERC
REGULATORY
Decrease of maximum transportation rate (as a percent)	10.00%
Additional decrease of unit rate (as a percent)	6.60%
Reduction in reservation rates (as a percent)	8.00%
Amount of agreed to issue a refund	$ 10
Provision for revenue sharing			$ 9
North Baja Pipeline, LLC \| FERC
REGULATORY
Reduce recourse rates in cost of service (as a percent)		11.00%
Tuscarora Gas Transmission Company \| Maximum
REGULATORY
Percentage of fair value exceeding its carrying value			10.00%
Great Lakes \| Maximum
REGULATORY
Percentage of fair value exceeding its carrying value			10.00%
Great Lakes \| FERC
REGULATORY
Goodwill			$ 260	$ 260