Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2019 reporting_unit
Summary of Significant Accounting Policies [Line Items]
Payment term	30 days
Number of reporting units for purposes of testing goodwill for impairment	3
2013 Omnibus Stock And Performance Incentive Plan Of Phillips 66
Summary of Significant Accounting Policies [Line Items]
Minimum time required for an award not to be subject to forfeiture	6 months
Eligible retirement age	55
Years of service	5 years
Minimum
Summary of Significant Accounting Policies [Line Items]
Length of construction period for interest capitalization	1 year