Consolidated Statement of Changes in Equity - USD ($) $ in Millions	Total	Accum. Other Comprehensive Loss	Net Investment— Predecessors	General Partner	Preferred Unitholders Public Public	Common Unitholders Public	Common Unitholders Non-public Phillips 66
Beginning Balance at Dec. 31, 2016	$ 1,566	$ (1)	$ 0	$ (704)	$ 0	$ 1,795	$ 476
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Predecessors	63		63
Net contributions to Phillips 66—Predecessors	666		666
Issuance of common units	1,204				737	467
Allocation of net investment—Predecessors and deemed net distributions to General Partner	(1,410)		$ (729)	(681)
Net income attributable to the Partnership	461			160	9	124	168
Quarterly cash distributions to unitholders and General Partner	(408)			(139)		(112)	(157)
Other contributions (distributions) from (to) Phillips 66	19			19
Ending Balance at Dec. 31, 2017	$ 2,161	(1)		$ (1,345)	$ 746	$ 2,274	$ 487
Beginning balance (in shares) at Dec. 31, 2016	109,369,312			2,187,386	0	43,134,902	64,047,024
Units Outstanding
Units issued in a public equity offering (in shares)	3,372,716					3,372,716
Units issued in private placement (in shares)	20,123,995				13,819,791	6,304,204
Units issued associated with acquisitions (in shares)	5,005,778			292,665			4,713,113
Ending balance (in shares) at Dec. 31, 2017	137,871,801			2,480,051	13,819,791	52,811,822	68,760,137
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Predecessors	$ 0
Issuance of common units	128					$ 128
Net income attributable to the Partnership	796			$ 240	$ 37	228	$ 291
Quarterly cash distributions to unitholders and General Partner	(613)			(216)	(37)	(158)	(202)
Other contributions (distributions) from (to) Phillips 66	7			7
Ending Balance at Dec. 31, 2018	$ 2,509	(1)		$ (1,313)	$ 746	$ 2,485	$ 592
Units Outstanding
Units issued in a public equity offering (in shares)	2,532,096					2,532,096
Ending balance (in shares) at Dec. 31, 2018	140,403,897			2,480,051	13,819,791	55,343,918	68,760,137
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Predecessors	$ 0
Issuance of common units	173					$ 173
Net income attributable to the Partnership	923			$ 140	$ 37	252	$ 494
Quarterly cash distributions to unitholders and General Partner	(756)			(206)	(37)	(192)	(321)
Conversion of GP economic interest	(4)			1,381			(1,385)
Other contributions (distributions) from (to) Phillips 66	(10)			(2)			(8)
Ending Balance at Dec. 31, 2019	$ 2,834	$ (1)		$ 0	$ 746	$ 2,717	$ (628)
Units Outstanding
Units issued in a public equity offering (in shares)	3,195,521					3,195,521
Units issued in conversion of GP economic interest (in shares)	98,519,949			(2,480,051)			101,000,000
Ending balance (in shares) at Dec. 31, 2019	242,119,367			0	13,819,791	58,539,439	169,760,137