Agreements and Transactions with Affiliates - Transactions with Affiliates (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Related Party Transaction [Line Items]
Operating and maintenance expense	$ 153	$ 178
Affiliated Entity \| Phillips 66
Related Party Transaction [Line Items]
Purchases and related costs	27	31
Operating and maintenance expense	4	4
Natural Gas, NGLs and Condensate [Member] \| Affiliated Entity \| Unconsolidated Affiliates
Related Party Transaction [Line Items]
Sales of natural gas, NGLs and condensate	9	14
Purchases and related costs	9	24
Natural Gas, NGLs and Condensate [Member] \| Affiliated Entity \| Phillips 66
Related Party Transaction [Line Items]
Sales of natural gas, NGLs and condensate	212	326
Natural Gas, NGLs and Condensate [Member] \| Affiliated Entity \| Enbridge
Related Party Transaction [Line Items]
Sales of natural gas, NGLs and condensate	1	0
Purchases and related costs	0	7
Transportation, Processing and Other [Member]
Related Party Transaction [Line Items]
Sales of natural gas, NGLs and condensate	112	115
Transportation, Processing and Other [Member] \| Affiliated Entity \| Unconsolidated Affiliates
Related Party Transaction [Line Items]
Sales of natural gas, NGLs and condensate	3	1
Purchases and related costs	215	195
Transportation, Processing and Other [Member] \| Affiliated Entity \| Phillips 66
Related Party Transaction [Line Items]
Purchases and related costs	$ 23	$ 14

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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