Income (loss) from disposal, excluding discontinued operations, before tax, excluding gain/loss on disposal

No definition available.

Name:	semg_Incomelossfromdisposalexcludingdiscontinuedoperationsbeforetaxexcludinggainlossondisposal
Namespace Prefix:	semg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount before tax of gain (loss) recognized on the sale or disposal of a disposal group. Excludes discontinued operations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2443-110228

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2941-110230

+ Details

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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

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

- Definition

The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3179-108585

+ Details

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

- Details

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- Details

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- Details

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Disposal of long-lived assets (Details) - USD ($) $ in Millions			9 Months Ended
	Apr. 12, 2018	Mar. 15, 2018	Sep. 30, 2018
SemMexico [Member]
Disposal of long-lived assets [Line Items]
Proceeds from Divestiture of Businesses		$ 70.7
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			$ 1.6
Income (loss) from disposal, excluding discontinued operations, before tax, excluding gain/loss on disposal			2.3
SemLogistics [Member]
Disposal of long-lived assets [Line Items]
Proceeds from Divestiture of Businesses	$ 73.1
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			0.4
Income (loss) from disposal, excluding discontinued operations, before tax, excluding gain/loss on disposal			5.4
Glass Mountain Pipeline LLC [Member]
Disposal of long-lived assets [Line Items]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			$ 1.4