Consolidated Statement of Changes in Equity - USD ($) $ in Millions	Total	Accum. Other Comprehensive Loss	General Partner	Preferred Units Public	Common Units Public	Common Units Non-public Phillips 66
Beginning Balance at Dec. 31, 2018	$ 2,509	$ (1)	$ (1,313)	$ 746	$ 2,485	$ 592
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common units	32				32
Net income	198		69	10	53	66
Quarterly cash distributions to unitholders and General Partner	(180)		(67)	(9)	(46)	(58)
Other contributions to Phillips 66	(4)		(4)
Ending Balance at Mar. 31, 2019	$ 2,554	(1)	$ (1,315)	$ 747	$ 2,523	$ 600
Beginning balance, Units (in shares) at Dec. 31, 2018	140,403,897		2,480,051	13,819,791	55,343,918	68,760,137
Units Outstanding [Roll Forward]
Units issued in public equity offerings (in shares)	622,032				622,032
Ending balance, Units (in shares) at Mar. 31, 2019	141,025,929		2,480,051	13,819,791	55,965,950	68,760,137
Beginning Balance at Dec. 31, 2019	$ 2,834	(1)	$ 0	$ 746	$ 2,717	$ (628)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common units	2				2
Net income	226			10	55	161
Quarterly cash distributions to unitholders and General Partner	(209)		$ 0	(9)	(51)	(149)
Ending Balance at Mar. 31, 2020	$ 2,853	$ (1)		$ 747	$ 2,723	$ (616)
Beginning balance, Units (in shares) at Dec. 31, 2019	242,119,367		0	13,819,791	58,539,439	169,760,137
Units Outstanding [Roll Forward]
Units issued in public equity offerings (in shares)	40,570				40,570
Ending balance, Units (in shares) at Mar. 31, 2020	242,159,937		0	13,819,791	58,580,009	169,760,137