Statement of Changes in Member's Equity (Unaudited) - NWP - USD ($) $ in Millions	Total	Northwest Pipeline LLC [Member]	Member's Capital Northwest Pipeline LLC [Member]	Retained Earnings Northwest Pipeline LLC [Member]
Balance at beginning of period at Dec. 31, 2023			$ 1,074	$ 59
Capital contributions from parent		$ 0	0
Net income	$ 1,033	96		96
Cash distributions to parent		76		(76)
Balance at end of period at Jun. 30, 2024		1,153	1,074	79
Balance at beginning of period at Mar. 31, 2024			1,074	79
Capital contributions from parent			0
Net income	401	43		43
Cash distributions to parent				(43)
Balance at end of period at Jun. 30, 2024		1,153	1,074	79
Balance at beginning of period at Dec. 31, 2024		1,163	1,074	89
Capital contributions from parent		(131)	131
Net income	1,237	91		91
Cash distributions to parent		64		(64)
Balance at end of period at Jun. 30, 2025		1,321	1,205	116
Balance at beginning of period at Mar. 31, 2025			1,159	111
Capital contributions from parent			46
Net income	$ 546	45		45
Cash distributions to parent				(40)
Balance at end of period at Jun. 30, 2025		$ 1,321	$ 1,205	$ 116