Phillps 66 Partners LP (Schedule of assets and liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Cash and cash equivalents	$ 1,614	$ 3,019
Equity investments	14,284	14,218
Net properties, plants and equipment		22,018
Phillips 66 Partners LP \| Phillips 66 Partners
Related Party Transaction [Line Items]
Cash and cash equivalents	286	1
Equity investments	2,961	2,448
Net properties, plants and equipment	3,349	3,052
Short-term debt	25	50
Long-term debt	$ 3,491	$ 2,998

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