CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
OPERATING REVENUES:
Total operating revenues	$ 115		$ 126	$ 326	$ 270
OPERATING EXPENSES:
Operating and maintenance	47		39	87	89
General and administrative	9		9	18	19
Depreciation and amortization	26		26	52	52
Total operating expenses	82		74	157	160
OPERATING INCOME	33		52	169	110
OTHER INCOME (EXPENSE):
Interest expense, net	(3)		(3)	(7)	(7)
Interest expense — related company	(4)		(8)	(10)	(17)
Other, net	0		3	0	(4)
INCOME BEFORE INCOME TAX EXPENSE (BENEFIT)	26		44	152	82
Income tax expense	0		1	0	(1)
NET INCOME	26	$ 126	43	152	83
OTHER COMPREHENSIVE INCOME, NET OF TAX
Actuarial gain relating to postretirement benefit plans	0	$ 6	4	6	9
COMPREHENSIVE INCOME	26		47	158	92
Natural Gas, US Regulated [Member]
OPERATING REVENUES:
Transportation and storage of natural gas	111		122	317	261
Product and Service, Other [Member]
OPERATING REVENUES:
Transportation and storage of natural gas	$ 4		$ 4	$ 9	$ 9