RELATED PARTY TRANSACTIONS (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
General Partner
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	$ 1		$ 2	$ 1
TransCanada Corporation | Great Lakes
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	8	8	16	16
Impact on the Partnership's net income	3	3	7	7
Amounts payable to TransCanada and its affiliates	3		3		4
Percentage of capital and operating costs charged by TransCanada's subsidiaries			100.00%
Transportation revenues from TransCanada and its affiliates	14	17	35	41
Percentage of transportation revenues to total revenues	49.00%	37.00%	54.00%	43.00%
Revenue from TransCanada and its affiliates included in the Partnership's equity earnings from Great Lakes	6	8	16	19
Great Lakes' receivables for transportation contracts with TransCanada and its affiliates	5		5		10
TransCanada Corporation | Northern Border
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	7	7	14	15
Impact on the Partnership's net income	4	3	7	7
Amounts payable to TransCanada and its affiliates	3		3		4
Percentage of capital and operating costs charged by TransCanada's subsidiaries			100.00%
TransCanada Corporation | GTN
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	7	7	14	14
Impact on the Partnership's net income	1	2	3	3
Amounts payable to TransCanada and its affiliates	3		3		3
Percentage of capital and operating costs charged by TransCanada's subsidiaries			100.00%
TransCanada Corporation | Bison
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	2	1	3	3
Impact on the Partnership's net income			1	1
Amounts payable to TransCanada and its affiliates	1		1		1
Percentage of capital and operating costs charged by TransCanada's subsidiaries			100.00%
TransCanada Corporation | North Baja
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	1	1	2	2
Impact on the Partnership's net income	1	1	2	2
Amounts payable to TransCanada and its affiliates					1
TransCanada Corporation | Tuscarora
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	1	1	2	2
Impact on the Partnership's net income	1	1	2	2
Amounts payable to TransCanada and its affiliates	$ 1		$ 1		$ 1