Condensed Consolidating Financial Information (Balance Sheet) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents	$ 1,221	$ 1,614
Accounts and notes receivable	4,559	8,510
Inventories	5,331	3,776
Prepaid expenses and other current assets	594	495
Total Current Assets	11,705	14,395
Investments and long-term receivables	13,635	14,571
Net properties, plants and equipment	24,051	23,786
Goodwill	1,425	3,270
Intangibles	880	869
Other assets	1,764	1,829
Total Assets	53,460	58,720
Liabilities and Equity
Accounts payable	5,322	8,575
Short-term debt	2,243	547
Accrued income and other taxes	703	979
Employee benefit obligations	301	710
Other accruals	1,960	835
Total Current Liabilities	10,529	11,646
Long-term debt	10,720	11,216
Asset retirement obligations and accrued environmental costs	635	638
Deferred income taxes	5,487	5,553
Employee benefit obligations	1,000	1,044
Other liabilities and deferred credits	1,450	1,454
Total Liabilities	29,821	31,551
Common stock	3,195	3,634
Retained earnings	19,168	22,064
Accumulated other comprehensive loss	(991)	(788)
Noncontrolling interests	2,267	2,259
Total Liabilities and Equity	53,460	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	30,738	33,082
Net properties, plants and equipment	0	0
Goodwill	0	0
Intangibles	0	0
Other assets	13	14
Total Assets	30,751	33,184
Liabilities and Equity
Accounts payable	0	0
Short-term debt	2,196	500
Accrued income and other taxes	0	0
Employee benefit obligations	0	0
Other accruals	134	65
Total Current Liabilities	2,330	565
Long-term debt	6,936	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	83	245
Total Liabilities	9,349	8,244
Common stock	3,195	3,634
Retained earnings	19,198	22,094
Accumulated other comprehensive loss	(991)	(788)
Noncontrolling interests	0	0
Total Liabilities and Equity	30,751	33,184
Reportable Legal Entities | Phillips 66 Company
Assets
Cash and cash equivalents	809	136
Accounts and notes receivable	3,114	6,334
Inventories	3,821	2,594
Prepaid expenses and other current assets	387	362
Total Current Assets	8,131	9,426
Investments and long-term receivables	24,454	25,039
Net properties, plants and equipment	13,738	13,676
Goodwill	1,047	2,853
Intangibles	744	732
Other assets	4,239	4,290
Total Assets	52,353	56,016
Liabilities and Equity
Accounts payable	5,296	7,024
Short-term debt	16	16
Accrued income and other taxes	303	386
Employee benefit obligations	271	648
Other accruals	1,620	850
Total Current Liabilities	7,506	8,924
Long-term debt	165	155
Asset retirement obligations and accrued environmental costs	460	460
Deferred income taxes	3,863	3,727
Employee benefit obligations	787	825
Other liabilities and deferred credits	9,782	8,975
Total Liabilities	22,563	23,066
Common stock	25,859	25,838
Retained earnings	4,922	7,900
Accumulated other comprehensive loss	(991)	(788)
Noncontrolling interests	0	0
Total Liabilities and Equity	52,353	56,016
Reportable Legal Entities | All Other Subsidiaries
Assets
Cash and cash equivalents	412	1,478
Accounts and notes receivable	3,726	4,148
Inventories	1,510	1,182
Prepaid expenses and other current assets	207	131
Total Current Assets	5,855	6,939
Investments and long-term receivables	10,173	10,989
Net properties, plants and equipment	10,313	10,110
Goodwill	378	417
Intangibles	136	137
Other assets	662	714
Total Assets	27,517	29,306
Liabilities and Equity
Accounts payable	2,307	3,609
Short-term debt	31	31
Accrued income and other taxes	400	593
Employee benefit obligations	30	62
Other accruals	548	249
Total Current Liabilities	3,316	4,544
Long-term debt	3,619	3,627
Asset retirement obligations and accrued environmental costs	175	178
Deferred income taxes	1,627	1,828
Employee benefit obligations	213	219
Other liabilities and deferred credits	5,799	5,465
Total Liabilities	14,749	15,861
Common stock	9,527	9,516
Retained earnings	1,453	1,940
Accumulated other comprehensive loss	(479)	(270)
Noncontrolling interests	2,267	2,259
Total Liabilities and Equity	27,517	29,306
Consolidating Adjustments
Assets
Cash and cash equivalents	0	0
Accounts and notes receivable	(2,281)	(2,058)
Inventories	0	0
Prepaid expenses and other current assets	0	0
Total Current Assets	(2,281)	(2,058)
Investments and long-term receivables	(51,730)	(54,539)
Net properties, plants and equipment	0	0
Goodwill	0	0
Intangibles	0	0
Other assets	(3,150)	(3,189)
Total Assets	(57,161)	(59,786)
Liabilities and Equity
Accounts payable	(2,281)	(2,058)
Short-term debt	0	0
Accrued income and other taxes	0	0
Employee benefit obligations	0	0
Other accruals	(342)	(329)
Total Current Liabilities	(2,623)	(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	(14,214)	(13,231)
Total Liabilities	(16,840)	(15,620)
Common stock	(35,386)	(35,354)
Retained earnings	(6,405)	(9,870)
Accumulated other comprehensive loss	1,470	1,058
Noncontrolling interests	0	0
Total Liabilities and Equity	$ (57,161)	$ (59,786)