| Document and Entity Information Document and Entity Information | Oct. 30, 2020 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Oct. 30, 2020 |
| Entity Registrant Name | Phillips 66 |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-35349 |
| Entity Tax Identification Number | 45-3779385 |
| Entity Address, Address Line One | 2331 CityWest Boulevard |
| Entity Address, City or Town | Houston |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 77042 |
| City Area Code | 281 |
| Local Phone Number | 293-6600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, $0.01 par value |
| Trading Symbol | PSX |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001534701 |
| Amendment Flag | false |
