Condensed Consolidating Financial Information (Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 1,614	$ 3,019
Accounts and notes receivable	8,510	6,173
Inventories	3,776	3,543
Prepaid expenses and other current assets	495	474
Total Current Assets	14,395	13,209
Investments and long-term receivables	14,571	14,421
Net properties, plants and equipment	23,786
Net properties, plants and equipment		22,018
Goodwill	3,270	3,270	$ 3,270
Intangibles	869	869
Other assets	1,829	515
Total Assets	58,720	54,302	$ 54,371
Liabilities and Equity
Accounts payable	8,575	6,586
Short-term debt	547	67
Accrued income and other taxes	979	1,116
Employee benefit obligations	710	724
Other accruals	835	442
Total Current Liabilities	11,646	8,935
Long-term debt	11,216	11,093
Asset retirement obligations and accrued environmental costs	638	624
Deferred income taxes	5,553	5,275
Employee benefit obligations	1,044	867
Other liabilities and deferred credits	1,454	355
Total Liabilities	31,551	27,149
Common stock	3,634	4,856
Retained earnings	22,064	20,489
Accumulated other comprehensive loss	(788)	(692)
Noncontrolling interests	2,259	2,500
Total Liabilities and Equity	58,720	54,302
Consolidating Adjustments
Assets
Cash and cash equivalents	0	0
Accounts and notes receivable	(2,058)	(1,293)
Inventories	0	0
Prepaid expenses and other current assets	0	0
Total Current Assets	(2,058)	(1,293)
Investments and long-term receivables	(54,539)	(50,919)
Net properties, plants and equipment	0
Net properties, plants and equipment		0
Goodwill	0	0
Intangibles	0	0
Other assets	(3,189)	(2)
Total Assets	(59,786)	(52,214)
Liabilities and Equity
Accounts payable	(2,058)	(1,293)
Short-term debt	0	0
Accrued income and other taxes	0	0
Employee benefit obligations	0	0
Other accruals	(329)	0
Total Current Liabilities	(2,387)	(1,293)
Long-term debt	0	0
Asset retirement obligations and accrued environmental costs	0	0
Deferred income taxes	(2)	(2)
Employee benefit obligations	0	0
Other liabilities and deferred credits	(13,231)	(8,598)
Total Liabilities	(15,620)	(9,893)
Common stock	(35,354)	(33,714)
Retained earnings	(9,870)	(9,592)
Accumulated other comprehensive loss	1,058	985
Noncontrolling interests	0	0
Total Liabilities and Equity	(59,786)	(52,214)
Phillips 66 | Reportable Legal Entities
Assets
Cash and cash equivalents	0	0
Accounts and notes receivable	86	9
Inventories	0	0
Prepaid expenses and other current assets	2	2
Total Current Assets	88	11
Investments and long-term receivables	33,082	32,712
Net properties, plants and equipment	0
Net properties, plants and equipment		0
Goodwill	0	0
Intangibles	0	0
Other assets	14	9
Total Assets	33,184	32,732
Liabilities and Equity
Accounts payable	0	0
Short-term debt	500	0
Accrued income and other taxes	0	0
Employee benefit obligations	0	0
Other accruals	65	66
Total Current Liabilities	565	66
Long-term debt	7,434	7,928
Asset retirement obligations and accrued environmental costs	0	0
Deferred income taxes	0	1
Employee benefit obligations	0	0
Other liabilities and deferred credits	245	55
Total Liabilities	8,244	8,050
Common stock	3,634	4,856
Retained earnings	22,094	20,518
Accumulated other comprehensive loss	(788)	(692)
Noncontrolling interests	0	0
Total Liabilities and Equity	33,184	32,732
Phillips 66 Company | Reportable Legal Entities
Assets
Cash and cash equivalents	136	1,648
Accounts and notes receivable	6,334	4,255
Inventories	2,594	2,489
Prepaid expenses and other current assets	362	373
Total Current Assets	9,426	8,765
Investments and long-term receivables	25,039	22,799
Net properties, plants and equipment	13,676
Net properties, plants and equipment		13,218
Goodwill	2,853	2,853
Intangibles	732	726
Other assets	4,290	335
Total Assets	56,016	48,696
Liabilities and Equity
Accounts payable	7,024	5,415
Short-term debt	16	11
Accrued income and other taxes	386	458
Employee benefit obligations	648	663
Other accruals	850	227
Total Current Liabilities	8,924	6,774
Long-term debt	155	54
Asset retirement obligations and accrued environmental costs	460	458
Deferred income taxes	3,727	3,541
Employee benefit obligations	825	676
Other liabilities and deferred credits	8,975	4,611
Total Liabilities	23,066	16,114
Common stock	25,838	24,960
Retained earnings	7,900	8,314
Accumulated other comprehensive loss	(788)	(692)
Noncontrolling interests	0	0
Total Liabilities and Equity	56,016	48,696
All Other Subsidiaries | Reportable Legal Entities
Assets
Cash and cash equivalents	1,478	1,371
Accounts and notes receivable	4,148	3,202
Inventories	1,182	1,054
Prepaid expenses and other current assets	131	99
Total Current Assets	6,939	5,726
Investments and long-term receivables	10,989	9,829
Net properties, plants and equipment	10,110
Net properties, plants and equipment		8,800
Goodwill	417	417
Intangibles	137	143
Other assets	714	173
Total Assets	29,306	25,088
Liabilities and Equity
Accounts payable	3,609	2,464
Short-term debt	31	56
Accrued income and other taxes	593	658
Employee benefit obligations	62	61
Other accruals	249	149
Total Current Liabilities	4,544	3,388
Long-term debt	3,627	3,111
Asset retirement obligations and accrued environmental costs	178	166
Deferred income taxes	1,828	1,735
Employee benefit obligations	219	191
Other liabilities and deferred credits	5,465	4,287
Total Liabilities	15,861	12,878
Common stock	9,516	8,754
Retained earnings	1,940	1,249
Accumulated other comprehensive loss	(270)	(293)
Noncontrolling interests	2,259	2,500
Total Liabilities and Equity	$ 29,306	$ 25,088