PARTNERS' EQUITY - ATM Equity Issuance Program (Details) - USD ($)	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
TC PipeLines GP, Inc. \| General Partner
Partners' Equity
Ownership interest in the Partnership (as a percent)	2.00%	2.00%
ATM Equity Issuance Program \| Common units
Partners' Equity
Units sold	368,448
Net proceeds from public offering of common units	$ 19,000,000
Sales agent commissions	186,000
ATM Equity Issuance Program \| TC PipeLines GP, Inc. \| General Partner
Partners' Equity
Equity contribution	$ 400,000

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

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

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- 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

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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

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- 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

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- 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

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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.

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No definition available.

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