Document and Entity Information	6 Months Ended
	Jun. 30, 2014	Jul. 25, 2014
Document and Entity Information
Entity Registrant Name	TC PIPELINES LP
Entity Central Index Key	0001075607
Document Type	10-Q
Document Period End Date	Jun. 30, 2014
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		62,327,766
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q2