RELATED PARTY TRANSACTIONS (Details) - USD ($) $ in Millions		3 Months Ended			4 Months Ended	12 Months Ended
	Apr. 11, 2013	Dec. 31, 2015	Mar. 31, 2015	Jun. 30, 2013	May. 03, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 01, 2015	Oct. 01, 2014	Jul. 01, 2013
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates		$ 5				$ 5	$ 15
Amount included in receivables from related party							1
Bison
Capital and operating costs charged to the pipeline systems and amount payable
Total cash call issued to fund debt repayment				$ 24
Bison | TransCanada
Capital and operating costs charged to the pipeline systems and amount payable
Equity contribution form former parent				$ 18
Great Lakes
Capital and operating costs charged to the pipeline systems and amount payable
Total cash call issued to fund debt repayment		$ 10	$ 9
Great Lakes | TransCanada
Capital and operating costs charged to the pipeline systems and amount payable
Ownership interest (as a percent)		53.55%				53.55%
Bison | TransCanada
Capital and operating costs charged to the pipeline systems and amount payable
Ownership interest (as a percent)				75.00%
General Partner | Reimbursement of costs of services provided
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged						$ 3	3	$ 3
TransCanada's subsidiaries | GTN
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates		$ 3				3	10
TransCanada's subsidiaries | GTN | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged						30	30	28
Impact on the Partnership's net income attributable to controlling interests						$ 25	$ 19	$ 19
Percentage of capital and operating costs charged						100.00%	100.00%	100.00%
TransCanada's subsidiaries | Northern Border
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates		5				$ 5	$ 10
TransCanada's subsidiaries | Northern Border | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged						$ 36	$ 35	$ 30
Percentage of capital and operating costs charged						100.00%	100.00%	100.00%
TransCanada's subsidiaries | Bison
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates							$ 2
TransCanada's subsidiaries | Bison | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged						$ 4	6	$ 5
Impact on the Partnership's net income attributable to controlling interests						$ 4	$ 4	$ 4
Percentage of capital and operating costs charged						100.00%	100.00%	100.00%
TransCanada's subsidiaries | Great Lakes
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates		3				$ 3	$ 9
Amount included in receivables from related party		17				17	15
TransCanada's subsidiaries | Great Lakes | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged						$ 30	$ 30	$ 31
Percentage of capital and operating costs charged						100.00%	100.00%	100.00%
TransCanada's subsidiaries | Great Lakes | Transportation contracts
Capital and operating costs charged to the pipeline systems and amount payable
Revenues from related party						$ 125	$ 71	$ 68
TransCanada's subsidiaries | Great Lakes | Transportation contracts | Total revenues | Customer concentration risk
Capital and operating costs charged to the pipeline systems and amount payable
Percent of total revenues						71.00%	49.00%	55.00%
TransCanada's subsidiaries | Great Lakes | Affiliated rental revenue
Capital and operating costs charged to the pipeline systems and amount payable
Revenues from related party						$ 2	$ 2	$ 1
TransCanada's subsidiaries | North Baja Pipeline, LLC
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates							1
TransCanada's subsidiaries | North Baja Pipeline, LLC | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged						5	5	4
Impact on the Partnership's net income attributable to controlling interests						5	4	4
TransCanada's subsidiaries | Tuscarora Gas Transmission Company
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates		1				1	1
TransCanada's subsidiaries | Tuscarora Gas Transmission Company | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged						4	4	4
Impact on the Partnership's net income attributable to controlling interests						4	4	4
TransCanada's subsidiaries | Northern Border | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Impact on the Partnership's net income attributable to controlling interests						14	16	14
TransCanada's subsidiaries | Great Lakes
Capital and operating costs charged to the pipeline systems and amount payable
Revenue from TransCanada and its affiliates included in the Partnership's equity earnings						59	34	32
TransCanada's subsidiaries | Great Lakes | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Impact on the Partnership's net income attributable to controlling interests						$ 13	13	$ 14
Former parent, TransCanada subsidiaries | Transaction between entities under common control | GTN
Capital and operating costs charged to the pipeline systems and amount payable
Interest acquired (as a percent)									30.00%		45.00%
Additional acquisition consideration relating to Carty Lateral project	$ 25
Former parent, TransCanada subsidiaries | Transaction between entities under common control | Bison
Capital and operating costs charged to the pipeline systems and amount payable
Interest acquired (as a percent)										30.00%	45.00%
ANR Pipeline Company | Great Lakes | Firm service between Michigan and Wisconsin
Capital and operating costs charged to the pipeline systems and amount payable
Deferred revenue related to services performed					$ 14		$ 9
Deferred revenue recognized		$ 23