Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Feb. 22, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	001-36710
Entity Registrant Name	Shell Midstream Partners, L.P.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-5223743
Entity Address, Address Line One	150 N. Dairy Ashford
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77079
City Area Code	832
Local Phone Number	337-2034
Title of 12(b) Security	Common Units, Representing Limited Partner Interests
Trading Symbol	SHLX
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1,518
Entity Common Stock, Shares Outstanding		393,289,537
Documents Incorporated by Reference	Documents incorporated by reference: None
Entity Central Index Key	0001610466
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false