Debt Instrument, Discount, Percentage

No definition available.

Name:	semg_DebtInstrumentDiscountPercentage
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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

Limit on potential increase in facility

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Line of Credit Facility, Ratio

+ References

No definition available.

+ Details

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- Definition

Long term debt.

+ References

No definition available.

+ Details

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- 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

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+ Details

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

- Definition

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

+ References

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+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of the required periodic payments applied to principal.

+ References

+ Details

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

- Definition

Amount, after accumulated amortization, of debt discount.

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+ Details

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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.

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+ 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

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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.

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+ Details

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Namespace Prefix:	us-gaap_
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

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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+ Details

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

- 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

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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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
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+ Details

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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.

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-Section S99
-Paragraph 2
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Balance Type:	debit
Period Type:	duration

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Period Type:

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- Details

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Period Type:

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Long-Term Debt (Details Textual) - USD ($) $ in Thousands					12 Months Ended
Long-Term Debt (Details Textual) - USD ($) $ in Thousands	Apr. 17, 2018	Sep. 20, 2017	Mar. 17, 2017	Mar. 15, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 26, 2018
Long Term Debt (Textual) [Abstract]
Gain (Loss) on Extinguishment of Debt					$ 0	$ (19,930)	$ 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					$ 24,335
Second Payment [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage
Long-term Debt, Gross					$ 0	565,868
Senior Unsecured Notes due 2021 [Member] \| Senior Notes [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage				7.50%
Debt Instrument, Face Amount				$ 300,000
HFOTCO Credit Facility [Member]
Long Term Debt (Textual) [Abstract]
Long-term Line of Credit								$ 75,000
HFOTCO Credit Facility [Member] \| Revolving Credit Facility [Member] \| Line of Credit [Member]
Long Term Debt (Textual) [Abstract]
Long-term Line of Credit					$ 0	60,000
Senior Unsecured Notes due 2025 [Member] \| Senior Notes [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage				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
Long-term Debt, Gross					$ 325,000	325,000
Senior unsecured notes due 2026 [Member] \| Senior Notes [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage		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
Long-term Debt, Gross					$ 300,000	300,000
Fair Value, Inputs, Level 3 [Member]
Long Term Debt (Textual) [Abstract]
Long-term Debt, Fair Value					$ 2,200,000
Second Payment [Member]
Long Term Debt (Textual) [Abstract]
Extinguishment of Debt, Amount	$ 579,600
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%
HFOTCO LLC [Member] \| Term Loan B [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage					5.28%
Debt Instrument, Periodic Payment, Principal					$ 1,500
Debt Instrument, Unamortized Discount								1,500
Long-term Debt, Gross					597,000	532,125		$ 600,000
Limit on potential increase in facility					$ 120,000
HFOTCO LLC [Member] \| Tax Exempt Notes Payable due 2050 [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage					3.399%
Long-term Debt, Gross					$ 225,000	$ 225,000
HFOTCO LLC [Member] \| Eurodollar [Member] \| Term Loan B [Member]
Long Term Debt (Textual) [Abstract]
Debt Instrument, Basis Spread on Variable Rate					2.75%
HFOTCO LLC [Member] \| Alternate Base Rate [Member] \| Term Loan B [Member]
Long Term Debt (Textual) [Abstract]
Debt Instrument, Basis Spread on Variable Rate					1.75%
HFOTCO LLC [Member] \| Maximum Super Senior Leverage Ratio [Member] \| Tax Exempt Notes Payable due 2050 [Member]
Long Term Debt (Textual) [Abstract]
Line of Credit Facility, Covenant Terms					3.50
HFOTCO LLC [Member] \| Minimum interest coverage ratio [Member] \| Tax Exempt Notes Payable due 2050 [Member]
Long Term Debt (Textual) [Abstract]
Line of Credit Facility, Covenant Terms					2.00