Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Supplemental Cash Flow Information [Abstract]
Cash capital expenditures and investments	$ 236	$ 634
Change in capital expenditure accruals	(2)	(2)
Total capital expenditures and investments	$ 234	$ 632

Cash outflows for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets as well as net cash outflows associated with the acquisition of investments.

No definition available.

Name:	psx_CapitalExpendituresAndInvestments
Namespace Prefix:	psx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration