PARTNERS' EQUITY (Details) (USD $) In Millions, except Share data, unless otherwise specified				0 Months Ended		12 Months Ended			12 Months Ended			0 Months Ended		12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	May 22, 2013 Common units	May 03, 2011 Common units	Dec. 31, 2013 Common units	Dec. 31, 2011 Common units	Dec. 31, 2012 Common units	Dec. 31, 2013 General Partner	Dec. 31, 2011 General Partner	Dec. 31, 2013 TC PipeLines GP, Inc. Common units	May 22, 2013 TC PipeLines GP, Inc. General Partner	May 03, 2011 TC PipeLines GP, Inc. General Partner	Dec. 31, 2013 TC PipeLines GP, Inc. General Partner	Dec. 31, 2013 TC PipeLines GP, Inc. Effective interest (combined common units and General Partner interests)	Dec. 31, 2012 TC PipeLines GP, Inc. Effective interest (combined common units and General Partner interests)	Dec. 31, 2011 TC PipeLines GP, Inc. Effective interest (combined common units and General Partner interests)	Dec. 31, 2013 TransCanada Common units
Ownership interests in the Partnership
Number of common units owned	62,300,000	53,500,000	53,500,000			62,327,766	53,472,766	53,472,766			5,797,106							11,287,725
Ownership interest in the Partnership (as a percent)						98.00%												17.80%
Ownership interest in the Partnership (as a percent)												2.00%	2.00%	2.00%	11.10%	12.60%	12.60%
Units sold in public offering				8,855,000	7,245,000
Units sold in public offering pursuant to exercise of underwriters' option				1,155,000
Price per common unit in public offering				$ 43.85	$ 47.58
Gross proceeds from public offering of common units				$ 388	$ 345
Net proceeds from public offering of common units				373	331	373	331
Capital contribution									$ 8	$ 7		$ 8	$ 7