RELATED PARTY TRANSACTIONS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018
Capital and operating costs charged to the pipeline systems and amount payable
Net amounts payable	$ 7			$ 6
Amount included in receivables from related party	4			2
General Partner | Reimbursement of costs of services provided
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	1		$ 1
TC Energy | Great Lakes
Capital and operating costs charged to the pipeline systems and amount payable
Net amounts payable	$ 5			3
Percentage of capital and operating costs charged	100.00%		100.00%
Amount included in receivables from related party	$ 18			18
TC Energy | Great Lakes | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	11		$ 9
Impact on the Partnership's net income attributable to controlling interests	$ 5		$ 4
Percentage of capital and operating costs charged	100.00%		100.00%
TC Energy | Great Lakes | Transportation contracts | Total net revenues | Customer concentration risk
Capital and operating costs charged to the pipeline systems and amount payable
Percent of total revenues	73.00%		68.00%
TC Energy | Northern Border
Capital and operating costs charged to the pipeline systems and amount payable
Net amounts payable	$ 4			3
Percentage of capital and operating costs charged	100.00%		100.00%
TC Energy | Northern Border | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	$ 9		$ 9
Impact on the Partnership's net income attributable to controlling interests	$ 4		$ 4
Percentage of capital and operating costs charged	100.00%		100.00%
TC Energy | PNGTS
Capital and operating costs charged to the pipeline systems and amount payable
Net amounts payable	$ 1			1
Percentage of capital and operating costs charged	100.00%		100.00%
TC Energy | PNGTS | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	$ 2		$ 2
Impact on the Partnership's net income attributable to controlling interests	$ 1		$ 1
Percentage of capital and operating costs charged	100.00%		100.00%
TC Energy | PNGTS | Transportation contracts
Capital and operating costs charged to the pipeline systems and amount payable
Amount included in receivables from related party	$ 0			0
Revenues from related party	0		$ 1
TC Energy | GTN
Capital and operating costs charged to the pipeline systems and amount payable
Net amounts payable	4			4
TC Energy | GTN | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	10		8
Impact on the Partnership's net income attributable to controlling interests	8		8
TC Energy | Bison
Capital and operating costs charged to the pipeline systems and amount payable
Net amounts payable				1
TC Energy | Bison | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	1		2
Impact on the Partnership's net income attributable to controlling interests	1		2
TC Energy | North Baja
Capital and operating costs charged to the pipeline systems and amount payable
Net amounts payable	1
TC Energy | North Baja | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	1		1
Impact on the Partnership's net income attributable to controlling interests	1		1
TC Energy | Tuscarora
Capital and operating costs charged to the pipeline systems and amount payable
Net amounts payable				$ 1
TC Energy | Tuscarora | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	1		1
Impact on the Partnership's net income attributable to controlling interests	1		$ 1
ANR Pipeline Company | Great Lakes | Transportation contracts
Capital and operating costs charged to the pipeline systems and amount payable
Contract term		15 years
Total contract value		$ 1,300
Affiliates | PNGTS | Construction of facilities
Capital and operating costs charged to the pipeline systems and amount payable
Reimbursement of costs	$ 71