Distribution To Holders Of Incentive Distribution Rights Waived

No definition available.

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

- References

No definition available.

+ Details

Name:	shlx_LessorOperatingLeaseNumberOfRenewalTerms
Namespace Prefix:	shlx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	shlx_NumberOfRevolvingCreditFacilities
Namespace Prefix:	shlx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

Name:	shlx_StatuteofLimitationsExpirationsNumberofDays
Namespace Prefix:	shlx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Costs of sales and operating expenses for the period incurred from transactions with related parties.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

+ Details

Name:	us-gaap_CostsAndExpensesRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Amount of cost for defined contribution plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

+ Details

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

- Definition

The expense in the period incurred with respect to protection provided by insurance entities against risks other than risks associated with production (which are allocated to cost of sales).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.4)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

+ Details

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

- Definition

Term of lessor's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888428&loc=SL77919359-209981

+ Details

Name:	us-gaap_LessorOperatingLeaseRenewalTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Term of lessor's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_LessorOperatingLeaseTermOfContract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of cost (reversal of cost) for other postretirement benefits. Excludes pension benefits.

+ References

No definition available.

+ Details

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

- Definition

Amount paid to managing member or general partner, affiliate of managing member or general partner, or affiliate of limited liability company (LLC) or limited partnership (LP) for administrative services provided to the LLC or LP, for example, but not limited to, salaries, rent, or overhead costs.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 17
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3367-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

+ Details

Name:	us-gaap_PaymentForAdministrativeFees
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=shlx_TransportationServicesOperatingLeasesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=shlx_TransportationServicesOperatingLeasesFiveYearTermsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=shlx_TransportationServicesOperatingLeasesOneYearTermsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_AffiliatedEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=shlx_ShellTreasuryCenterWestIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=shlx_RefineryGasPipelineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=shlx_FiveYearFixedFacilityFixedRateDueMarch12022Member
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:	dei_LegalEntityAxis=shlx_OdysseyPipelineL.L.C.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Related Party Transactions - Additional Information (Details) $ in Millions		3 Months Ended				9 Months Ended	12 Months Ended
	Nov. 03, 2014 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($) term	Mar. 31, 2018 USD ($)	Sep. 30, 2018 credit_facility	Dec. 31, 2019 USD ($)	Dec. 31, 2018
Related Party Transaction [Line Items]
Statute of limitations expirations, number of days	60 days
Health and life insurance costs				$ 2.0	$ 2.0
Defined contribution benefit plan costs				1.0	1.0
Reimbursement of cost and expenses				7.0	4.0
Operations and maintenance – related parties				$ 14.0	13.0
Transportation Services Operating Leases
Related Party Transaction [Line Items]
Initial term				10 years
Transportation Services Operating Leases, Five Year Terms
Related Party Transaction [Line Items]
Initial term				10 years
Number of additional terms \| term				2
Additional term				5 years
Transportation Services Operating Leases, One Year Terms
Related Party Transaction [Line Items]
Initial term				10 years
Number of additional terms \| term				10
Additional term				1 year
SPLC
Related Party Transaction [Line Items]
General insurance expense				$ 4.0	$ 4.0
Distributions to holders of incentive distribution rights waived				17.0
Shell Treasury Center West Inc
Related Party Transaction [Line Items]
Number of revolving credit facilities \| credit_facility						4
Refinery Gas Pipeline
Related Party Transaction [Line Items]
Reimbursement of cost and expenses				$ 0.6
Five Year Revolver \| Shell Treasury Center West Inc
Related Party Transaction [Line Items]
Debt instrument term						5 years
Five Year Fixed Facility \| Shell Treasury Center West Inc
Related Party Transaction [Line Items]
Debt instrument term						5 years
Shell Pipeline Company L P
Related Party Transaction [Line Items]
Payment of general and administrative fee	$ 11.0
Odyssey Pipeline L.L.C. (“Odyssey”)
Related Party Transaction [Line Items]
Noncontrolling interest				29.00%				29.00%
Zydeco Pipeline Company LLC (“Zydeco”)
Related Party Transaction [Line Items]
Noncontrolling interest				7.50%				7.50%
Scenario, Forecast \| SPLC
Related Party Transaction [Line Items]
Distributions to holders of incentive distribution rights waived		$ 16.0	$ 17.0				$ 50.0