Debt Instrument, Early Prepayment Fee

No definition available.

Name:	shlx_DebtInstrumentEarlyPrepaymentFee
Namespace Prefix:	shlx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=123466204&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- 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

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28555-108399

+ Details

Name:	us-gaap_DeferredFinanceCostsGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1D
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28555-108399

+ Details

Name:	us-gaap_DeferredFinanceCostsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of interest expense incurred on a debt or other obligation to related party.

+ References

No definition available.

+ Details

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

- Definition

Amount of cash paid for interest, excluding capitalized interest, classified as operating activity. Includes, but is not limited to, payment to settle zero-coupon bond for accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=123431023&loc=d3e4297-108586

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 17
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3367-108585

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3536-108585

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=shlx_A2021TenYearFixedFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
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_DebtInstrumentAxis=shlx_TenYearFixedFacilityMember
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:	srt_CounterpartyNameAxis=shlx_ShellTreasuryCenterWestIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=shlx_SevenYearFixedFacilityDueJuly2025Member
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_DebtInstrumentAxis=shlx_FiveYearRevolverDueDecember2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Related Party Debt - Narrative (Details) - USD ($)									12 Months Ended
Related Party Debt - Narrative (Details) - USD ($)	Mar. 23, 2021	Mar. 16, 2021	Jun. 06, 2019	Jun. 04, 2019	Aug. 01, 2018	Jul. 31, 2018	Dec. 01, 2017	Mar. 01, 2017	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Line Of Credit Facility [Line Items]
Interest and fee expenses associated with borrowings									$ 82,000,000	$ 90,000,000	$ 92,000,000
Interest paid									81,000,000	92,000,000	$ 88,000,000
Debt instrument term	5 years
Maximum borrowing capacity									3,560,000,000	3,590,000,000
Debt issuance costs, net					$ 0
Long-term debt, carrying value									2,694,000,000	2,694,000,000
Long-term debt, fair value									$ 2,849,000,000	$ 2,928,000,000
2021 Ten Year Fixed Facility
Line Of Credit Facility [Line Items]
Debt instrument term	10 years	10 years
2021 Ten Year Fixed Facility \| Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument term		10 years							10 years
Maximum borrowing capacity		$ 600,000,000
Fixed interest rate		2.96%
Debt issuance costs, net		$ 0
2021 Ten Year Fixed Facility \| Revolving Credit Facility \| Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Debt instrument term									10 years
Ten Year Fixed Facility \| Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument term			10 years	10 years					10 years
Debt issuance costs, net				$ 0
Ten Year Fixed Facility \| Revolving Credit Facility \| Affiliated Entity \| Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Maximum borrowing capacity				$ 600,000,000
Fixed interest rate				4.18%
Ten Year Fixed Facility \| Revolving Credit Facility \| Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Debt instrument term									10 years
Seven Year Fixed Facility \| Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument term						7 years			7 years
Maximum borrowing capacity						$ 600,000,000
Fixed interest rate						4.06%
Debt issuance costs						$ 1,000,000
Seven Year Fixed Facility \| Revolving Credit Facility \| Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Debt instrument term									7 years
Five Year Revolver due July 2023 \| Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument term					5 years				5 years
Maximum borrowing capacity					$ 760,000,000
Fixed interest rate					0.19%
Weighted average interest rate									1.28%
Five Year Revolver due July 2023 \| Revolving Credit Facility \| Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Debt instrument term									5 years
Five Year Revolver due December 2022 \| Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument term							5 years		5 years
Five Year Revolver due December 2022 \| Revolving Credit Facility \| Affiliated Entity \| Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Maximum borrowing capacity							$ 1,000,000,000
Debt issuance costs							$ 2,000,000
Unused capacity commitment fee percentage							0.19%
Weighted average interest rate									1.47%
Five Year Revolver due December 2022 \| Revolving Credit Facility \| Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Debt instrument term									5 years
Five Year Fixed Facility \| Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument term	5 years							5 years	5 years
Five Year Fixed Facility \| Revolving Credit Facility \| Affiliated Entity \| Shell Treasury Center West Inc
Line Of Credit Facility [Line Items]
Early prepayment fee	$ 2,000,000