ORGANIZATION (Details 2)	0 Months Ended		12 Months Ended
	May 22, 2013	May 22, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Partners' Equity
Number of common units			63,600,000	62,300,000	53,500,000
Common Units (Limited Partners)
Partners' Equity
Number of common units			63,561,546	62,327,766	53,472,766
Limited partner interest (as a percent)			98.00%
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%
TC PipeLines GP, Inc. | Common Units (Limited Partners)
Partners' Equity
Number of common units			5,797,106
TC PipeLines GP, Inc. | Common units and General Partner interest combined
Partners' Equity
Ownership interest in the Partnership (as a percent)			10.90%	11.10%	12.60%
TransCanada | Common Units (Limited Partners)
Partners' Equity
Number of common units			11,287,725
Limited partner interest (as a percent)			17.40%
TransCanada Corporation and subsidiaries | Common units and General Partner interest combined
Partners' Equity
Ownership interest in the Partnership (as a percent)			28.30%