GOODWILL AND REGULATORY (Details) - USD ($) $ in Millions			3 Months Ended		11 Months Ended	12 Months Ended		24 Months Ended	47 Months Ended	54 Months Ended
	Dec. 06, 2018	Dec. 01, 2018	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2021	Dec. 31, 2022	Jun. 30, 2024	Dec. 31, 2020	Oct. 16, 2018	Dec. 31, 2017
REGULATORY
Provision for revenue sharing							$ 10
Goodwill impairment charge							59
Goodwill			$ 71				71						$ 130
Great Lakes | FERC
REGULATORY
Decrease in rate (as a percent)									2.00%
GTN | FERC
REGULATORY
Decrease in rate (as a percent)						10.00%		6.60%
Amount agreed to issue as refund to customers from January 1 to October 31, 2018												$ 10
Provision for revenue sharing			1	$ 9
Settlement rate reduced (as a percent)											8.30%
Northern Border | FERC
REGULATORY
Decrease in rate (as a percent)					2.00%					2.00%
Tuscarora
REGULATORY
Goodwill			23				23
North Baja
REGULATORY
Decrease in rate (as a percent)		10.80%
Number of contracts negotiated (as a percent)		90.00%
Tuscarora
REGULATORY
Decrease in rate (as a percent)	1.70%
Goodwill impairment charge							59
Goodwill			$ 82				$ 82