Cash Received From General Partner For Additional Shares Issued

No definition available.

Name:	shlx_CashReceivedFromGeneralPartnerForAdditionalSharesIssued
Namespace Prefix:	shlx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Contribution from our general partner for additional shares issued in order for our general partner to maintain its 2.0% general partner interest.

+ References

No definition available.

+ Details

Name:	shlx_ContributionFromGeneralPartnerForAdditionalSharesIssued
Namespace Prefix:	shlx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Gross Proceeds From Issuance Of Public Offering

+ References

No definition available.

+ Details

Name:	shlx_GrossProceedsFromIssuanceOfPublicOffering
Namespace Prefix:	shlx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Placement agent fees in connection with the private placement.

+ References

No definition available.

+ Details

Name:	shlx_PlacementFees
Namespace Prefix:	shlx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
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:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Monetary value of the issuance of new units of limited partnership interest in a public offering.

+ 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=27012166&loc=d3e187085-122770

Reference 2: 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=27012166&loc=d3e187171-122770

+ Details

Name:	us-gaap_PartnersCapitalAccountPublicSaleOfUnits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of units sold in a private placement of each class of partners' capital account. Units represent shares of ownership of the general, limited, and preferred partners.

+ References

+ Details

Name:	us-gaap_PartnersCapitalAccountUnitsSoldInPrivatePlacement
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of units sold in a public offering of each class of partners' capital account. Units represent shares of ownership of the general, limited, and preferred partners.

+ References

+ Details

Name:	us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow for cost incurred directly with the issuance of an equity security.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsOfStockIssuanceCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow associated with the amount received from entity's raising of capital via private rather than public placement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfPrivatePlacement
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Per share or per unit amount of equity securities issued.

+ References

No definition available.

+ Details

Name:	us-gaap_SharesIssuedPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=shlx_FiveYearRevolverDueDecember2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=shlx_FiveYearRevolverDueJuly2023Member
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:

- Details

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

- Details

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

(Deficit) Equity - Public Offerings and Private Placement (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended		12 Months Ended
	Feb. 06, 2018	Sep. 15, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Units issued in connection with public offering (in units)						36,764,707
Net proceeds from equity offerings						$ 973	$ 278
Contributions from general partner	$ 14	$ 3				20	6
Consideration for units issued in connection with private placement					$ 0	$ 20	6
Five Year Revolver Due December 2022
Class of Stock [Line Items]
Debt instrument term					5 years
Repayments of Debt					$ 726
Five Year Revolver due July 2023
Class of Stock [Line Items]
Debt instrument term					5 years
Repayments of Debt					$ 247
Common units - SPLC
Class of Stock [Line Items]
Units issued in connection with private placement (in units)	11,029,412		5,200,000	94,925	1,000,000,000
Common units per share (in units per share)	$ 27.20		$ 26.96	$ 31.51
Net proceeds from private equity placement	$ 300		$ 140	$ 3
Consideration for units issued in connection with private placement	$ 6
Common units - SPLC \| General Public
Class of Stock [Line Items]
Units issued in connection with public offering (in units)	25,000,000	5,170,000				25,000,000
Net proceeds from equity offerings	$ 673	$ 135
Gross proceeds from public offering	$ 680
Common units per share (in units per share)	$ 27.20
Underwriter fees	$ 6
Placement fees	$ 1
Common units - SPLC \| Shell Pipeline Company L P
Class of Stock [Line Items]
Units issued in connection with public offering (in units)						11,029,412
General Partner
Class of Stock [Line Items]
Units issued in connection with private placement (in units)	225,091		106,122	1,938
Units issued in connection with public offering (in units)	510,204	105,510				735,295
Consideration for units issued in connection with private placement			$ 3
General Partner \| General Partner Interest
Class of Stock [Line Items]
Aggregate percentage of interest					2.00%
General Partner \| Shell Pipeline Company L P
Class of Stock [Line Items]
Net proceeds from equity offerings							0
Contributions from general partner						$ 20	$ 6
General Partner \| Shell Pipeline Company L P \| General Partner Interest
Class of Stock [Line Items]
Aggregate percentage of interest	2.00%	2.00%			2.00%