Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

+ Details

Name:	us-gaap_ClassOfStockLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage investment held by the managing member or general partner of the limited liability company (LLC) or limited partnership (LP).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

+ Details

Name:	us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of ownership interest of different classes of partners in limited partnership.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

+ Details

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

- Definition

The number of each class of partnership units outstanding at the balance sheet date. Units represent shares of ownership of the general, limited, and preferred partners.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04.16(a))
-URI http://asc.fasb.org/extlink&oid=120401414&loc=d3e603758-122996

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04.16(b))
-URI http://asc.fasb.org/extlink&oid=120401414&loc=d3e603758-122996

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 5
-Subparagraph (SAB TOPIC 4.F)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187171-122770

+ Details

Name:	us-gaap_PartnersCapitalAccountUnits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_PartnerTypeOfPartnersCapitalAccountAxis=us-gaap_GeneralPartnerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=shlx_ShellPipelineCompanyLPMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=shlx_GeneralPartnerInterestMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PartnerTypeOfPartnersCapitalAccountAxis=us-gaap_LimitedPartnerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=shlx_LimitedPartnerInterestMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PartnerTypeOfPartnersCapitalAccountAxis=shlx_CommonUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

(Deficit) Equity - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Apr. 01, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Partners' capital		$ (494)	$ (481)
General Partner SPLC
Class of Stock [Line Items]
Units canceled (in units)		0	0	4,761,012
Partners' capital				$ (4,000)
General Partner SPLC \| Shell Pipeline Company L P \| General Partner Interest
Class of Stock [Line Items]
Aggregate percentage of interest	2.00%
Limited Partner \| Shell Pipeline Company L P \| Limited Partner Interest
Class of Stock [Line Items]
Aggregate percentage of interest	98.00%
Common Units \| Shell Pipeline Company L P
Class of Stock [Line Items]
Units canceled (in units)		269,457,304	269,457,304		109,457,304