ACQUISITIONS (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended		1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended	0 Months Ended		1 Months Ended			1 Months Ended
	May 31, 2011	Dec. 31, 2011	Jul. 13, 2011 Senior revolving credit facility	May 31, 2011 General Partner	Dec. 31, 2012 General Partner	May 31, 2011 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	May 31, 2011 GTN and Bison TransCanada Subsidiaries	May 03, 2011 GTN and Bison TransCanada Subsidiaries	May 03, 2011 GTN TransCanada Subsidiaries	May 31, 2011 Bison TransCanada Subsidiaries	May 03, 2011 Bison TransCanada Subsidiaries	Mar. 25, 2011 Yuma Lateral Asset Acquisition TransCanada Corporation	Mar. 05, 2010 Yuma Lateral Asset Acquisition TransCanada Corporation Maximum
Asset acquisition
Interest acquired by the Partnership (as a percent)												25.00%		25.00%
Purchase price											$ 605	$ 405		$ 200
Acquired debt												81
Percentage of acquired debt												25.00%
Future commitments related to acquisitions													9
Additional payment to TransCanada						23
Purchase price recorded as working capital							1
Cash paid											539				2
Number of common units sold in public offering	7,245,000					7,245,000
Price per common unit issued	$ 47.58					$ 47.58
Net proceeds from issuance of common units	331					331
Amount drawn on credit facility to finance acquisition								61	125
Maximum borrowing capacity			250					400	250
Contribution by General Partners										7
General partner ownership interest in the partnership (as a percent)				2.00%	2.00%
Cash on hand											15
Excess purchase price paid recorded as reduction to Partner's equity		(134)					(131)
Payment to be made to TransCanada																$ 2