ACQUISITIONS (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended		0 Months Ended		12 Months Ended						0 Months Ended			12 Months Ended	0 Months Ended	12 Months Ended				0 Months Ended				3 Months Ended	12 Months Ended			0 Months Ended				0 Months Ended
	Dec. 31, 2013		May 22, 2013 Common units	May 03, 2011 Common units	Dec. 31, 2013 Common units	Dec. 31, 2011 Common units	Dec. 31, 2013 General Partner	Dec. 31, 2011 General Partner	Dec. 31, 2013 Senior Credit Facility	Jul. 02, 2013 Senior Credit Facility	Jul. 02, 2013 Term loans	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	May 03, 2011 GTN and Bison	Dec. 31, 2013 GTN and Bison		Dec. 31, 2011 GTN and Bison		May 03, 2011 GTN and Bison Bridge loan facility	May 03, 2011 GTN and Bison Senior revolving credit facility	Jul. 02, 2013 GTN and Bison Former parent, TransCanada subsidiaries Transaction between entities under common control	May 03, 2011 GTN and Bison Former parent, TransCanada subsidiaries Transaction between entities under common control	Dec. 31, 2011 GTN and Bison Former parent, TransCanada subsidiaries Transaction between entities under common control	Dec. 31, 2013 GTN and Bison Former parent, TransCanada subsidiaries Transaction between entities under common control	Dec. 31, 2012 GTN and Bison Former parent, TransCanada subsidiaries Transaction between entities under common control	Dec. 31, 2011 GTN and Bison Former parent, TransCanada subsidiaries Transaction between entities under common control	Jul. 02, 2013 GTN and Bison Former parent, TransCanada subsidiaries Transaction between entities under common control Carrying value	Jul. 02, 2013 GTN Former parent, TransCanada subsidiaries Transaction between entities under common control	May 03, 2011 GTN Former parent, TransCanada subsidiaries Transaction between entities under common control	Dec. 31, 2013 GTN Former parent, TransCanada subsidiaries Transaction between entities under common control Accounts payable to affiliates	Jul. 22, 2013 Bison Former parent, TransCanada subsidiaries Transaction between entities under common control	Jul. 02, 2013 Bison Former parent, TransCanada subsidiaries Transaction between entities under common control	May 03, 2011 Bison Former parent, TransCanada subsidiaries Transaction between entities under common control	Mar. 25, 2011 Yuma Lateral Asset Acquisition	Mar. 05, 2010 Yuma Lateral Asset Acquisition TransCanada
Acquisition
Interest acquired by the Partnership (as a percent)																													45.00%	25.00%			45.00%	25.00%
Purchase price																						$ 1,050	$ 605						$ 750	$ 405			$ 300	$ 200
Working capital adjustments																						17	23	1											2
Acquired debt																													146	81
Cash paid																921	[1]	539	[1]			921	539
Future commitments related to acquisitions																																		9
Units sold in public offering			8,855,000	7,245,000											7,245,000
Price per common unit in public offering			$ 43.85	$ 47.58											$ 47.58
Net proceeds from issuance of common units			373	331	373	331									331
Borrowings under the facility											500									61	125
Capital contribution							8	7				8	7										7
General partner ownership interest in the partnership (as a percent)												2.00%	2.00%	2.00%
Cash on hand used in acquisition																							15
Excess purchase price paid recorded as reduction to Partner's equity					268	131	6	3															131
Maximum borrowing capacity									500	500	500									400	250
Contingent additional payment, maximum																													25							2
Contingent consideration																															25
Recorded purchase price
Current assets																						67
Property, plant and equipment, net																						1,792
Other assets																						1
Current liabilities																						(20)
Other liabilities																						(21)
Long-term debt																						(325)
Net assets acquired																						1,494
Non-controlling interest																												(448)
Pre-existing 25% interest in each of GTN and Bison																												(374)
Carrying value of acquired 45% interest in each of GTN and Bison																						672
Excess purchase price over net assets acquired																						274							262				12
Total cash consideration including $25 million Carty Lateral consideration payable																						946
Pre-existing interest acquired by the partnership (as a percent)																													25.00%				25.00%
Increase in the net income attributable to common units resulting from retrospective consolidation																									26	55	59
Amount received from TransCanada subsidiary as a post-closing construction expenditures adjustment	$ 1	[1]																														$ 1

[1] (a) Recast as discussed in Note 2 and Note 6.