Amount of cash or stock or unit payment to a limited liability corporation managing member or limited partnership general partner after the end of the accounting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 45

-Paragraph 73

-URI http://asc.fasb.org/extlink&oid=6926462&loc=SL5163674-159010

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 45

-Paragraph 72

-URI http://asc.fasb.org/extlink&oid=6926462&loc=SL5163672-159010

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 55

-Paragraph 103

-URI http://asc.fasb.org/extlink&oid=6926531&loc=SL5199526-159011

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

NET INCOME PER COMMON UNIT (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Apr. 02, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Partners' Equity
Incentive distributions allocated to the General Partner		$ 1		$ 2
TC PipeLines GP, Inc. \| General Partner
Partners' Equity
General partner interest (as a percent)	2.00%	2.00%	2.00%	2.00%	2.00%