Consolidated Balance Sheet (Parenthetical) - shares	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
General partner—Phillips 66 units issued (in shares)	0		2,480,051
General partner—Phillips 66 units outstanding (in shares)	0		2,480,051
Public
Preferred units, issued (in shares)	13,819,791		13,819,791
Preferred units, outstanding (in shares)	13,819,791		13,819,791
Common Units | Public
Common units issued (in shares)		58,539,439	55,343,918
Common Units | Non-public | Phillips 66
Common units outstanding (in shares)	169,760,137		68,760,137