Represents the number of financial institutions (Managers) acting as sales agents.

No definition available.

Name:	tcp_NumberOfFinancialInstitutionsActingAsSalesAgents
Namespace Prefix:	tcp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of sales agents (Managers) required to be in agreement with the entity for a sale of equity other than by means of ordinary brokers' transactions on a stock exchange at market prices or in block transactions.

+ References

No definition available.

+ Details

Name:	tcp_OtherEquitySalesMethodNumberOfManagersInAgreement
Namespace Prefix:	tcp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Authorized amount of issuance of new units of limited partnership interest in a public offering.

+ References

No definition available.

+ Details

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

- Definition

Percentage investment held by the managing member or general partner of the limited liability company (LLC) or limited partnership (LP).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

+ Details

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

- Definition

Total contributions made by each class of partners (i.e., general, limited and preferred partners).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187171-122770

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

+ Details

Name:	us-gaap_PartnersCapitalAccountContributions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Monetary value of the issuance of new units of limited partnership interest in a public offering, net of offering costs. This is a parenthetical disclosure.

+ References

+ Details

Name:	us-gaap_PartnersCapitalAccountPublicSaleOfUnitsNetOfOfferingCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of units sold in a public offering of each class of partners' capital account. Units represent shares of ownership of the general, limited, and preferred partners.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 5
-Subparagraph (SAB TOPIC 4.F)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187171-122770

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph 16
-Subparagraph a, b
-Article 6

+ Details

Name:	us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow for cost incurred directly with the issuance of an equity security.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsOfStockIssuanceCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_ScheduleOfCapitalizationEquityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_PartnerTypeOfPartnersCapitalAccountAxis=us-gaap_GeneralPartnerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=tcp_TCPipeLinesGeneralPartnershipIncorporatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tcp_SaleOfLimitedPartnershipUnitsAxis=tcp_AtMarketEquityIssuanceProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LimitedPartnersCapitalAccountByClassAxis=tcp_LimitedPartnerCommonUnitMember
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:

PARTNERS' EQUITY - ATM Equity Issuance Program (Details 2) shares in Millions, $ in Millions			1 Months Ended	12 Months Ended
	Apr. 01, 2015 USD ($)	May. 22, 2013	Aug. 31, 2014 USD ($) Institution	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013
Partners' Equity
Equity contribution				$ 2.0
General Partner
Partners' Equity
Equity contribution	$ 2.0			$ 2.0
TC PipeLines GP, Inc. \| General Partner
Partners' Equity
Ownership interest in the Partnership (as a percent)	2.00%	2.00%		2.00%	2.00%	2.00%
ATM Equity Issuance Program \| Common units
Partners' Equity
Number of financial institutions \| Institution			5
Aggregate offering price of units			$ 200.0
Units sold \| shares				0.7	1.3
Net proceeds from public offering of common units				$ 43.0	$ 71.0
Sales agent commissions				0.4	1.0
ATM Equity Issuance Program \| TC PipeLines GP, Inc. \| General Partner
Partners' Equity
Equity contribution				$ 1.0	$ 2.0
ATM Equity Issuance Program \| Minimum \| Common units
Partners' Equity
Number of managers to agree with equity sale method \| Institution			1