Statement of Cash Flows (Unaudited) - NWP - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	$ 1,312	$ 1,088
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, depletion, and amortization	1,190	1,088
Increase (Decrease) in Operating Capital [Abstract]
Increase (Decrease) in Inventories	(61)	(3)
Increase (Decrease) in Other Current Assets	(36)	12
Other current liabilities	150	(76)
Other Operating Activities, Cash Flow Statement	(77)	(151)
Net cash provided (used) by operating activities	2,883	2,513
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net cash provided (used) by financing activities	154	(1,552)
Net Cash Provided by (Used in) Investing Activities [Abstract]
Capital expenditures (1)	(1,984)	(1,123)
Net cash provided (used) by investing activities	(2,194)	(3,056)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total	843	(2,095)
Cash and cash equivalents at beginning of year	60	2,150
Cash and cash equivalents at end of period	903	55
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Property, Plant and Equipment, Additions	(2,041)	(1,141)
Capital expenditures	(1,984)	(1,123)
Northwest Pipeline LLC [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	91	96
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, depletion, and amortization	59	54
Increase (Decrease) in Allowance for Equity Funds Used During Construction	(3)	(3)
Increase (Decrease) in Operating Capital [Abstract]
Increase (Decrease) in Accounts Receivable, Related Parties	0	1
Increase (Decrease) in Accounts and Other Receivables	3	6
Increase (Decrease) in Other Current Assets	1	0
Increase (Decrease) in Accounts Payable, Trade	(2)	(2)
Increase (Decrease) in Accounts Payable, Related Parties	(4)	(5)
Other current liabilities	(3)	3
Other Operating Activities, Cash Flow Statement	(26)	(14)
Net cash provided (used) by operating activities	116	136
Net Cash Provided by (Used in) Financing Activities [Abstract]
Cash distributions to parent	(64)	(76)
Cash contributions from parent	131	0
Increase Decrease In Advances From Affiliates	(26)	0
Net cash provided (used) by financing activities	41	(76)
Net Cash Provided by (Used in) Investing Activities [Abstract]
Capital expenditures (1)	(92)	(94)
Contributions in aid of construction	5	7
Payments for (Proceeds from) Removal Costs	(6)	(1)
IncreaseDecreaseInAdvancesToAffiliates	(64)	28
Net cash provided (used) by investing activities	(157)	(60)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total	0	0
Cash and cash equivalents at beginning of year	0	0
Cash and cash equivalents at end of period	0	0
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Property, Plant and Equipment, Additions	(89)	(101)
Increase (Decrease) in Accounts Payable And Accrued Liabilities Related To Capital Expenditures	(3)	7
Capital expenditures	$ (92)	$ (94)

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