Debt Instrument, Discount, Percentage

No definition available.

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- Definition

Debt Instrument Redemption Price Percentage of Principal

+ References

No definition available.

+ Details

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- Definition

DebtInstrumentRedemptionPricePriorto RedemptionDatesBasisSpreadonVariableDiscount Rate

+ References

No definition available.

+ Details

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- Definition

Debt Instrument Redemption Price, Prior to Redemption Dates, Premium, Percentage

+ References

No definition available.

+ Details

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- Definition

Debt Instrument Redemption Price, Upon Change in Control, Percentage

+ References

No definition available.

+ Details

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- Definition

Long term debt.

+ References

No definition available.

+ Details

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- Definition

Amount of restricted net assets of consolidated and unconsolidated subsidiaries as of the end of the most recently completed fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e)(3)(ii))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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Balance Type:	debit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
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+ Details

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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/presentationRef
-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=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Amount of the required periodic payments applied to principal.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount.

+ References

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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Gross amount of debt extinguished.

+ References

No definition available.

+ Details

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

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

Description of the conditions for borrowing under the credit facility including the nature of any restrictions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
-Paragraph 1
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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

No definition available.

+ Details

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

- Definition

The excess of the (1) fair value of consideration transferred to the holders of a security in excess of (2) the carrying amount of the security reported on the registrant's balance sheet, which will be deducted from net earnings to derive net earnings available to common shareholders. This amount is generally an adjustment considered in the computation of earnings per share.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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- Details

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- Details

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- Details

Name:	us-gaap_DebtInstrumentAxis=semg_HFOTCOCreditFacilityMember
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- Details

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Long-Term Debt (Details Textual) $ in Thousands, MXN in Millions				12 Months Ended
	Sep. 20, 2017 USD ($)	Mar. 17, 2017 USD ($)	Mar. 15, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2017 MXN
Long Term Debt (Textual) [Abstract]
Gain (Loss) on Extinguishment of Debt				$ (19,930)	$ 0	$ 0
Redemption Premium				15,900
Write off of Deferred Debt Issuance Cost				$ 3,600
Senior Notes [Member]
Long Term Debt (Textual) [Abstract]
Debt Instrument Redemption Price Percentage of Principal				35.00%
Debt Instrument Redemption Price, Prior to Redemption Dates, Premium, Percentage				1.00%
Early redemption premium				101.00%
Revolving Credit Facility [Member]
Long Term Debt (Textual) [Abstract]
Maximum borrowing capacity				$ 1,000,000
Letters of credit outstanding				$ 39,385
Second Payment [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage				8.00%			8.00%
Senior Unsecured Notes due 2021 [Member] \| Senior Notes [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage			7.50%	7.50%			7.50%
Debt Instrument, Face Amount			$ 300,000
HFOTCO Credit Facility [Member] \| Revolving Credit Facility [Member] \| Line of Credit [Member]
Long Term Debt (Textual) [Abstract]
Maximum borrowing capacity				$ 75,000
Line of Credit Facility, Covenant Terms				7.50
Senior Unsecured Notes due 2025 [Member] \| Senior Notes [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage		6.375%		6.375%			6.375%
Debt Instrument, Face Amount		$ 325,000
Debt Instrument, Discount, Percentage		98.467%
Debt Instrument, Unamortized Discount		$ 5,000
Proceeds from Issuance of Debt		315,100
Debt Issuance Costs, Gross		4,900
Senior unsecured notes due 2026 [Member] \| Senior Notes [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage	7.25%			7.25%			7.25%
Debt Instrument, Face Amount	$ 300,000
Debt Instrument, Discount, Percentage	98.453%
Debt Instrument, Unamortized Discount	$ 4,600
Proceeds from Issuance of Debt	290,300
Debt Issuance Costs, Gross	$ 5,100
HFOTCO LLC [Member]
Long Term Debt (Textual) [Abstract]
Amount of Restricted Net Assets for Consolidated and Unconsolidated Subsidiaries				$ 1,100,000
HFOTCO LLC [Member] \| Term Loan B [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage				5.19%			5.19%
Debt Instrument, Periodic Payment, Principal				$ 1,400
HFOTCO LLC [Member] \| Tax Exempt Notes Payable due 2050 [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage				2.3525%			2.3525%
SemMexico [Member] \| Letter of Credit [Member]
Long Term Debt (Textual) [Abstract]
Letters of credit outstanding				$ 14,870			MXN 292.8
SemMexico [Member] \| MXP facility [Member]
Long Term Debt (Textual) [Abstract]
Maximum borrowing capacity				3,600			MXN 70.0
Fair Value, Inputs, Level 3 [Member]
Long Term Debt (Textual) [Abstract]
Long-term Debt, Fair Value				$ 2,900,000
Tender Offer [Member] \| Senior Unsecured Notes due 2021 [Member]
Long Term Debt (Textual) [Abstract]
Extinguishment of Debt, Amount			$ 290,000
Notes called [Member] \| Senior Unsecured Notes due 2021 [Member]
Long Term Debt (Textual) [Abstract]
Extinguishment of Debt, Amount		$ 10,000
US Treasury Rate [Member]
Long Term Debt (Textual) [Abstract]
Debt Instrument Redemption Price, Prior to Redemption Dates, Basis Spread on Variable Discount Rate				5000.00%
Maximum Super Senior Leverage Ratio [Member] \| HFOTCO LLC [Member] \| Tax Exempt Notes Payable due 2050 [Member]
Long Term Debt (Textual) [Abstract]
Line of Credit Facility, Covenant Terms				3.50
Minimum interest coverage ratio [Member] \| HFOTCO LLC [Member] \| Tax Exempt Notes Payable due 2050 [Member]
Long Term Debt (Textual) [Abstract]
Line of Credit Facility, Covenant Terms				2.00