Earnings per Share (Summary of Earnings Per Share Calculation) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic
Income from continuing operations attributable to Phillips 66									$ 1,555	$ 4,227	$ 4,056
Income allocated to participating securities									(6)	(6)	(7)
Income from continuing operations available to common stockholders									1,549	4,221	4,049
Discontinued operations									0	0	706
Net income available to common stockholders									$ 1,549	$ 4,221	$ 4,755
Weighted-average common shares outstanding (thousands): (in shares)									523,250	537,602	561,859
Effect of stock-based compensation (in shares)									4,281	4,753	4,043
Weighted-average commons shares outstanding - basic (in shares)									527,531	542,355	565,902
Income from continuing operations attributable to Phillips 66 (in dollars per share)									$ 2.94	$ 7.78	$ 7.15
Discontinued operations (in dollars per share)									0.00	0.00	1.25
Net Income Attributable to Phillips 66 Per Share of Common Stock (in dollars)	$ 0.31	$ 0.97	$ 0.94	$ 0.72	$ 1.21	$ 2.92	$ 1.85	$ 1.80	$ 2.94	$ 7.78	$ 8.40
Diluted
Income allocated to participating securities									$ (5)	$ 0	$ 0
Income allocated to participating securities									1,550	4,227	4,056
Net income available to common stockholders									$ 1,550	$ 4,227	$ 4,762
Effect of stock-based compensation									2,535	4,622	5,602
Weighted-average common shares outstanding—EPS									530,066	546,977	571,504
Income from continuing operations attributable to Phillips 66 (in dollars per share)									$ 2.92	$ 7.73	$ 7.10
Discontinued operations (in dollars per share)									0.00	0.00	1.23
Net Income Attributable to Phillips 66 Per Share of Common Stock (in dollars)	$ 0.31	$ 0.96	$ 0.93	$ 0.72	$ 1.20	$ 2.90	$ 1.84	$ 1.79	$ 2.92	$ 7.73	$ 8.33