Agreements and Transactions with Affiliates - Transactions with Affiliates (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Related Party Transaction [Line Items]
Operating and maintenance expense	$ 148	$ 182	$ 301	$ 360
Affiliated Entity \| Phillips 66
Related Party Transaction [Line Items]
Purchases and related costs	10	50	37	81
Operating and maintenance expense	2	3	6	7
Natural Gas, NGLs and Condensate [Member] \| Affiliated Entity \| Unconsolidated Affiliates
Related Party Transaction [Line Items]
Sales of natural gas, NGLs and condensate	12	4	21	18
Purchases and related costs	11	11	20	35
Natural Gas, NGLs and Condensate [Member] \| Affiliated Entity \| Phillips 66
Related Party Transaction [Line Items]
Sales of natural gas, NGLs and condensate	157	290	369	616
Natural Gas, NGLs and Condensate [Member] \| Affiliated Entity \| Enbridge
Related Party Transaction [Line Items]
Sales of natural gas, NGLs and condensate	0	0	1	0
Purchases and related costs	0	7	0	14
Operating and maintenance expense	1	0	1	0
Transportation, Processing and Other [Member]
Related Party Transaction [Line Items]
Sales of natural gas, NGLs and condensate	109	110	221	225
Transportation, Processing and Other [Member] \| Affiliated Entity \| Unconsolidated Affiliates
Related Party Transaction [Line Items]
Sales of natural gas, NGLs and condensate	3	0	6	1
Purchases and related costs	209	190	424	385
Transportation, Processing and Other [Member] \| Affiliated Entity \| Phillips 66
Related Party Transaction [Line Items]
Purchases and related costs	$ 21	$ 14	$ 44	$ 28

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
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