RELATED PARTY TRANSACTIONS - Summary of related party transactions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Accounts payable to affiliates	$ 6		$ 8
Great Lakes | TC Energy
Related Party Transaction [Line Items]
Accounts payable to affiliates	4		5
Great Lakes | TC Energy | Capital and operating costs
Related Party Transaction [Line Items]
Costs charged	11	$ 11
Impact on the Partnership's net income attributable to controlling interests	$ 4	5
Percentage of capital and operating costs charged	100.00%
Northern Border | TC Energy
Related Party Transaction [Line Items]
Accounts payable to affiliates	$ 3		4
Northern Border | TC Energy | Capital and operating costs
Related Party Transaction [Line Items]
Costs charged	10	9
Impact on the Partnership's net income attributable to controlling interests	$ 4	4
Percentage of capital and operating costs charged	100.00%
GTN | TC Energy
Related Party Transaction [Line Items]
Accounts payable to affiliates	$ 5		5
GTN | TC Energy | Capital and operating costs
Related Party Transaction [Line Items]
Costs charged	12	10
Impact on the Partnership's net income attributable to controlling interests	8	8
Bison | TC Energy
Related Party Transaction [Line Items]
Accounts payable to affiliates	0		0
Bison | TC Energy | Capital and operating costs
Related Party Transaction [Line Items]
Costs charged	0	1
Impact on the Partnership's net income attributable to controlling interests	0	1
North Baja | TC Energy
Related Party Transaction [Line Items]
Accounts payable to affiliates	0		1
North Baja | TC Energy | Capital and operating costs
Related Party Transaction [Line Items]
Costs charged	1	1
Impact on the Partnership's net income attributable to controlling interests	1	1
Tuscarora | TC Energy
Related Party Transaction [Line Items]
Accounts payable to affiliates	0		0
Tuscarora | TC Energy | Capital and operating costs
Related Party Transaction [Line Items]
Costs charged	1	1
Impact on the Partnership's net income attributable to controlling interests	1	1
PNGTS | TC Energy
Related Party Transaction [Line Items]
Accounts payable to affiliates	1		$ 1
PNGTS | TC Energy | Capital and operating costs
Related Party Transaction [Line Items]
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%