CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Generated from Operations
Net income (loss)	$ 301	$ 298	$ (165)
Depreciation	89	78	97
Impairment of long-lived assets (Note 7)	0	0	537
Impairment of goodwill (Note 4)	0	0	59
Amortization of Debt Issuance Costs and Discounts	2	2	2
Amortization of realized loss on derivative instrument (Note 19)	0	0	1
Equity earnings from equity investments (Note 5)	(170)	(160)	(173)
Distributions from equity investments	196	200	188
Change in other long-term liabilities	1	(1)	(2)
Equity allowance for funds used during construction	(10)	(2)	(1)
Change in operating working capital (Note 15)	4	(3)	(3)
Cash Generated from Operations	413	412	540
Investing Activities
Distribution received as return on investment	29	58	10
Capital expenditures	(278)	(75)	(40)
Other	(1)	(1)	4
Investing Activities	(262)	(32)	(35)
Financing Activities
Distributions paid (Note 14)	(189)	(189)	(218)
Distributions paid to Class B units (Notes 10 and 14)	(8)	(13)	(15)
Distributions paid to non-controlling interests	(23)	(22)	(14)
Common unit issuance, net (Note 10)	0	0	40
Long-term debt issued, net of discount (Note 8)	385	30	219
Long-term debt repaid (Note 8)	(199)	(136)	(516)
Debt issuance costs	0	0	(1)
Financing Activities	(34)	(330)	(505)
Increase/(decrease) in cash and cash equivalents	117	50	0
Cash and cash equivalents, beginning of year	83	33	33
Cash and cash equivalents, end of year	200	83	33
Interest payments paid	75	87	94
State income taxes paid	1	2	1
Supplemental information about non-cash investing and financing activities
Accrued capital expenditures, net	8	4	2
Great Lakes
Cash Generated from Operations
Equity earnings from equity investments (Note 5)	(56)	(51)	(59)
Investing Activities
Investment of interests	(10)	(10)	(9)
Iroquois
Cash Generated from Operations
Equity earnings from equity investments (Note 5)	(38)	(40)	(46)
Investing Activities
Investment of interests	(2)	(4)	0
Distribution received as return on investment	29	8	10
Northern Border
Cash Generated from Operations
Equity earnings from equity investments (Note 5)	(76)	(69)	(68)
Investing Activities
Distribution received as return on investment	$ 0	$ 50	$ 0