Capital lease monthly payment.

No definition available.

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

- Definition

Capital Lease Rate Increase Decrease

+ References

No definition available.

+ Details

Name:	shlx_CapitalLeaseRateIncreaseDecrease
Namespace Prefix:	shlx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Lessee Leasing Arrangement, Capital Lease, Renewal Term

+ References

No definition available.

+ Details

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

- Definition

Lessee Leasing Arrangements, Capital Lease, Term of Contract

+ References

No definition available.

+ Details

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

- Definition

Total costs accrued as of the balance sheet date for environmental loss contingencies.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 25
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

+ Details

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

- Definition

Aggregate carrying amount of the estimated litigation liability for known or estimated probable loss from litigation, which may include attorneys' fees and other litigation costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

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 210.5-02.25)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

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

- Details

Name:	srt_CounterpartyNameAxis=shlx_StateofWashingtonDepartmentofEcologyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Commitments and Contingencies (Details) - USD ($) $ in Millions	Jul. 01, 2018	Sep. 01, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Loss Contingencies [Line Items]
Accrual for settlement of litigation					$ 2.3
Traffic rate increase	4.40%
Initial term of contract		10 years
Renewal term		1 year
State of Washington Department of Ecology
Loss Contingencies [Line Items]
Environmental accrual			$ 0.3	$ 0.3
Port Neches Tank Lease
Loss Contingencies [Line Items]
Monthly lease payment		$ 0.4