Condensed Consolidating Financial Information (Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents	$ 1,462	$ 1,614
Accounts and notes receivable	5,963	8,510
Inventories	4,897	3,776
Prepaid expenses and other current assets	500	495
Total Current Assets	12,822	14,395
Investments and long-term receivables	13,767	14,571
Net properties, plants and equipment	23,489	23,786
Goodwill	1,425	3,270
Intangibles	849	869
Other assets	1,929	1,829
Total Assets	54,281	58,720
Liabilities and Equity
Accounts payable	5,457	8,575
Short-term debt	1,860	547
Accrued income and other taxes	1,229	979
Employee benefit obligations	443	710
Other accruals	1,524	835
Total Current Liabilities	10,513	11,646
Long-term debt	12,666	11,216
Asset retirement obligations and accrued environmental costs	644	638
Deferred income taxes	5,507	5,553
Employee benefit obligations	1,394	1,044
Other liabilities and deferred credits	1,252	1,454
Total Liabilities	31,976	31,551
Common stock	3,253	3,634
Retained earnings	17,436	22,064
Accumulated other comprehensive loss	(967)	(788)
Noncontrolling interests	2,583	2,259
Total Liabilities and Equity	54,281	58,720
Reportable Legal Entities | Phillips 66
Assets
Cash and cash equivalents	0	0
Accounts and notes receivable	0	86
Inventories	0	0
Prepaid expenses and other current assets	0	2
Total Current Assets	0	88
Investments and long-term receivables	30,358	33,082
Net properties, plants and equipment	0	0
Goodwill	0	0
Intangibles	0	0
Other assets	12	14
Total Assets	30,370	33,184
Liabilities and Equity
Accounts payable	0	0
Short-term debt	1,498	500
Accrued income and other taxes	0	0
Employee benefit obligations	0	0
Other accruals	159	65
Total Current Liabilities	1,657	565
Long-term debt	8,939	7,434
Asset retirement obligations and accrued environmental costs	0	0
Deferred income taxes	0	0
Employee benefit obligations	0	0
Other liabilities and deferred credits	22	245
Total Liabilities	10,618	8,244
Common stock	3,253	3,634
Retained earnings	17,466	22,094
Accumulated other comprehensive loss	(967)	(788)
Noncontrolling interests	0	0
Total Liabilities and Equity	30,370	33,184
Reportable Legal Entities | Phillips 66 Company
Assets
Cash and cash equivalents	665	136
Accounts and notes receivable	4,477	6,334
Inventories	3,421	2,594
Prepaid expenses and other current assets	255	362
Total Current Assets	8,818	9,426
Investments and long-term receivables	25,272	25,039
Net properties, plants and equipment	12,783	13,676
Goodwill	1,047	2,853
Intangibles	717	732
Other assets	4,207	4,290
Total Assets	52,844	56,016
Liabilities and Equity
Accounts payable	5,282	7,024
Short-term debt	15	16
Accrued income and other taxes	480	386
Employee benefit obligations	392	648
Other accruals	1,304	850
Total Current Liabilities	7,473	8,924
Long-term debt	156	155
Asset retirement obligations and accrued environmental costs	463	460
Deferred income taxes	3,566	3,727
Employee benefit obligations	1,166	825
Other liabilities and deferred credits	10,990	8,975
Total Liabilities	23,814	23,066
Common stock	25,886	25,838
Retained earnings	4,111	7,900
Accumulated other comprehensive loss	(967)	(788)
Noncontrolling interests	0	0
Total Liabilities and Equity	52,844	56,016
Reportable Legal Entities | All Other Subsidiaries
Assets
Cash and cash equivalents	797	1,478
Accounts and notes receivable	3,905	4,148
Inventories	1,476	1,182
Prepaid expenses and other current assets	245	131
Total Current Assets	6,423	6,939
Investments and long-term receivables	10,990	10,989
Net properties, plants and equipment	10,706	10,110
Goodwill	378	417
Intangibles	132	137
Other assets	713	714
Total Assets	29,342	29,306
Liabilities and Equity
Accounts payable	2,594	3,609
Short-term debt	347	31
Accrued income and other taxes	749	593
Employee benefit obligations	51	62
Other accruals	425	249
Total Current Liabilities	4,166	4,544
Long-term debt	3,571	3,627
Asset retirement obligations and accrued environmental costs	181	178
Deferred income taxes	1,944	1,828
Employee benefit obligations	228	219
Other liabilities and deferred credits	5,664	5,465
Total Liabilities	15,754	15,861
Common stock	9,582	9,516
Retained earnings	1,743	1,940
Accumulated other comprehensive loss	(320)	(270)
Noncontrolling interests	2,583	2,259
Total Liabilities and Equity	29,342	29,306
Consolidating Adjustments
Assets
Cash and cash equivalents	0	0
Accounts and notes receivable	(2,419)	(2,058)
Inventories	0	0
Prepaid expenses and other current assets	0	0
Total Current Assets	(2,419)	(2,058)
Investments and long-term receivables	(52,853)	(54,539)
Net properties, plants and equipment	0	0
Goodwill	0	0
Intangibles	0	0
Other assets	(3,003)	(3,189)
Total Assets	(58,275)	(59,786)
Liabilities and Equity
Accounts payable	(2,419)	(2,058)
Short-term debt	0	0
Accrued income and other taxes	0	0
Employee benefit obligations	0	0
Other accruals	(364)	(329)
Total Current Liabilities	(2,783)	(2,387)
Long-term debt	0	0
Asset retirement obligations and accrued environmental costs	0	0
Deferred income taxes	(3)	(2)
Employee benefit obligations	0	0
Other liabilities and deferred credits	(15,424)	(13,231)
Total Liabilities	(18,210)	(15,620)
Common stock	(35,468)	(35,354)
Retained earnings	(5,884)	(9,870)
Accumulated other comprehensive loss	1,287	1,058
Noncontrolling interests	0	0
Total Liabilities and Equity	$ (58,275)	$ (59,786)