Phillips 66 Partners LP (Schedule of Assets and Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Cash and cash equivalents	$ 1,221	$ 1,614
Phillips 66 Partners LP \| Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Cash and cash equivalents	92	286
Equity investments	3,136	2,961
Net properties, plants and equipment	3,410	3,349
Short-term debt	25	25
Long-term debt	$ 3,491	$ 3,491

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