Employee Benefit Plans (Narrative) (Details) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($) $ / shares	Dec. 31, 2012 shares	Dec. 31, 2009	Dec. 31, 2008	May. 31, 2013 shares	Jan. 02, 2009
Employee Benefit Plans (Textual) [Abstract]
Net actuarial gains and losses, Percent amortized		10.00%
Health care cost trend rate, ultimate, percentage		5.00%
Year of measurement of the accumulated postretirement benefit obligation assumes a health care cost trend rate, after decline		2023
Percentage-point change in the assumed health care cost trend rate		1.00%
Maximum employee contribution of eligible pay, Percent		75.00%
Semi-annual discretionary company contribution target, Percent		2.00%
Total expense related to participants in the Savings Plan		$ 134	$ 112	$ 111
Minimum service period to avoid award forfeiture, in months		6 months
Date of performance awards authorization relative to grant date					3 years
Weighted average grant date fair value of options granted | $ / shares	[1]	$ 18.84		$ 18.95
Intrinsic value of options exercised	[1]	$ 60		$ 89
United States Pension Plans of U S Entity Defined Benefit [Member]
Employee Benefit Plans (Textual) [Abstract]
Expected future employer contributions next fiscal year		50
Foreign Pension Plans Defined Benefit [Member]
Employee Benefit Plans (Textual) [Abstract]
Expected future employer contributions next fiscal year		$ 50
Other Postretirement Benefit Plans, Defined Benefit [Member]
Employee Benefit Plans (Textual) [Abstract]
Health care cost trend rate, percentage		6.75%
Tax-Qualified Pension Plans [Member]
Employee Benefit Plans (Textual) [Abstract]
Projected benefit obligation, Tax-qualified pension plans with projected benefit obligations in excess of plan assets		$ 3,005	3,189
Accumulated benefit obligation, Tax-qualified pension plans with projected benefit obligations in excess of plan assets		2,676	2,815
Fair value of plan assets, Tax-qualified pension plans with projected benefit obligations in excess of plan assets		2,183	2,295
Unfunded Nonqualified Key Employee Pension Plans [Member]
Employee Benefit Plans (Textual) [Abstract]
Projected benefit obligation, Tax-qualified pension plans with projected benefit obligations in excess of plan assets		137	107
Accumulated benefit obligation, Tax-qualified pension plans with projected benefit obligations in excess of plan assets		$ 112	$ 83
Equity Securities [Member]
Employee Benefit Plans (Textual) [Abstract]
Target allocations for plan assets		62.00%
Debt Securities [Member]
Employee Benefit Plans (Textual) [Abstract]
Target allocations for plan assets		37.00%
Other Types of Investments [Member]
Employee Benefit Plans (Textual) [Abstract]
Target allocations for plan assets		1.00%
Stock Options [Member]
Employee Benefit Plans (Textual) [Abstract]
Stock option terms in years		10 years
Weighted-average remaining contractual terms of vested options		5 years 7 months 6 days
Weighted-average remaining contractual terms of exercisable options		4 years 11 months 16 days
Cash received from the exercise of options		$ 31
Tax benefit from the exercise of options		8
Unrecognized compensation expense from unvested awards held by employees		$ 3
Weighted-average period for recognition of unrecognized compensation expense from unvested awards		21 months
Longest period for recognition of unrecognized compensation expense from unvested awards		25 months
Restricted Stock Units (RSUs) [Member]
Employee Benefit Plans (Textual) [Abstract]
Award vesting rights per anniversary date		one-third
Unrecognized compensation expense from unvested awards held by employees		$ 46
Weighted-average period for recognition of unrecognized compensation expense from unvested awards		20 months
Longest period for recognition of unrecognized compensation expense from unvested awards		35 months
Number of shares of common stock to be issued per stock unit | shares		1
Weighted average grant date fair value | $ / shares		$ 74.09		$ 73.28
Aggregate fair value		$ 107		$ 116
Performance Shares [Member]
Employee Benefit Plans (Textual) [Abstract]
Unrecognized compensation expense from unvested awards held by employees		$ 15
Weighted-average period for recognition of unrecognized compensation expense from unvested awards		36 months
Longest period for recognition of unrecognized compensation expense from unvested awards		11 years
Eligible retirement age							55		55
Years of service						5 years	5 years
Number of shares of common stock to be issued per stock unit | shares					1
Weighted average grant date fair value | $ / shares	[2]	$ 74.14		$ 72.26
Aggregate fair value	[2]	$ 37		$ 13
Minimum [Member]
Employee Benefit Plans (Textual) [Abstract]
Minimum participant contribution to Savings Plan to be eligible for Success Share, Percent		1.00%
Semi-annual discretionary company contribution, Percent		0.00%
Minimum service period to avoid award forfeiture, in months		6 months
Maximum [Member]
Employee Benefit Plans (Textual) [Abstract]
Company match of participant's contributions of eligible pay, Percent		5.00%
Semi-annual discretionary company contribution, Percent		6.00%
Employees Eligible for Retirement [Member] | Stock Options [Member]
Employee Benefit Plans (Textual) [Abstract]
Award vesting period		6 months
Employees Eligible for Retirement [Member] | Restricted Stock Units (RSUs) [Member]
Employee Benefit Plans (Textual) [Abstract]
Award vesting period		6 months
Awards Vesting Ratably Over Three Years On Anniversary Of Grant Date [Member] | Stock Options [Member]
Employee Benefit Plans (Textual) [Abstract]
Award vesting period		3 years
Before April 30, 2012 [Member] | Restricted Stock Units (RSUs) [Member]
Employee Benefit Plans (Textual) [Abstract]
Award vesting period		5 years
Before April 30, 2012 [Member] | Awards Vesting Over Five Years, First Third Of Units [Member] | Restricted Stock Units (RSUs) [Member]
Employee Benefit Plans (Textual) [Abstract]
Award vesting period		36 months
Before April 30, 2012 [Member] | Awards Vesting Over Five Years, Second Third Of Units [Member] | Restricted Stock Units (RSUs) [Member]
Employee Benefit Plans (Textual) [Abstract]
Award vesting period		48 months
Before April 30, 2012 [Member] | Awards Vesting Over Five Years, Final Third Of Units [Member] | Restricted Stock Units (RSUs) [Member]
Employee Benefit Plans (Textual) [Abstract]
Award vesting period		60 months
2013 Omnibus Stock And Performance Incentive Plan Of Phillips 66 [Member]
Employee Benefit Plans (Textual) [Abstract]
Common stock issuable under P66 Omnibus Plan, maximum | shares								45,000,000
2013 Omnibus Stock And Performance Incentive Plan Of Phillips 66 [Member] | Cliff Vesting [Member] | Restricted Stock Units (RSUs) [Member]
Employee Benefit Plans (Textual) [Abstract]
Award vesting period		3 years

[1] All option awards presented in this table are for Phillips 66 stock only, including those awards held by ConocoPhillips employees.

[2] All PSU awards presented in this table are for Phillips 66 stock only, including those awards held by ConocoPhillips employees.