RELATED PARTY TRANSACTIONS (Details) (USD $) In Millions, unless otherwise specified			12 Months Ended
	May 31, 2011 GTN	May 31, 2011 Bison	Dec. 31, 2012 General Partner	Dec. 31, 2011 General Partner	Dec. 31, 2010 General Partner	Dec. 31, 2012 TransCanada Corporation Great Lakes	Dec. 31, 2011 TransCanada Corporation Great Lakes	Dec. 31, 2010 TransCanada Corporation Great Lakes	Dec. 31, 2012 TransCanada Corporation Northern Border	Dec. 31, 2011 TransCanada Corporation Northern Border	Dec. 31, 2010 TransCanada Corporation Northern Border	Dec. 31, 2012 TransCanada Corporation GTN	Dec. 31, 2011 TransCanada Corporation GTN	Dec. 31, 2012 TransCanada Corporation Bison	Dec. 31, 2011 TransCanada Corporation Bison	Dec. 31, 2012 TransCanada Corporation North Baja	Dec. 31, 2011 TransCanada Corporation North Baja	Dec. 31, 2010 TransCanada Corporation North Baja	Dec. 31, 2012 TransCanada Corporation Tuscarora Gas Transmission Company	Dec. 31, 2011 TransCanada Corporation Tuscarora Gas Transmission Company	Dec. 31, 2010 TransCanada Corporation Tuscarora Gas Transmission Company
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates			$ 3	$ 2	$ 2	$ 33	$ 31	$ 30	$ 31	$ 29	$ 26	$ 29	$ 22	$ 6	$ 8	$ 4	$ 4	$ 4	$ 4	$ 5	$ 4
Impact on the Partnership's net income						15	14	13	14	13	13	7	5	1	1	4	4	3	4	5	4
Amounts payable to TransCanada and its affiliates						4	3		4	3		3	3	1	1	1	1		1	1
Percentage of capital and operating costs charged by TransCanada's subsidiaries						100.00%			100.00%			100.00%		100.00%
Ownership interest at the end of the period (as a percent)	25.00%	25.00%
Transportation revenues from TransCanada and its affiliates						77	81	149
Percentage of transportation revenues to total revenues						42.00%	32.00%	57.00%
Affiliated rental revenue						1	1	1
Revenue from TransCanada and its affiliates included in the Partnership's equity earnings from Great Lakes						36	38	69
Great Lakes' receivables for transportation contracts with TransCanada and its affiliates						$ 10	$ 7