Face (par) amount of debt instrument at time of issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Investments, Loans and Long-Term Receivables (Dakota Access, LLC and Energy Transfer Crude Oil, Company, LLC) (Details) - USD ($)	Mar. 31, 2020	Mar. 31, 2019
Dakota Access and ETCO
Schedule of Equity Method Investments [Line Items]
Maximum exposure, undiscounted, co-venturers	$ 2,525,000,000
Senior Notes \| Dakota Access, LLC
Schedule of Equity Method Investments [Line Items]
Debt issued and guaranteed		$ 2,500,000,000
Variable Interest Entity, Primary Beneficiary \| Phillips 66 Partners LP \| Dakota Access and ETCO
Schedule of Equity Method Investments [Line Items]
Maximum exposure, undiscounted	$ 631,000,000