SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 2) (USD $) In Millions, unless otherwise specified	1 Months Ended	6 Months Ended
Mar. 31, 2014	Jun. 30, 2014
Significant Accounting Policies [Line Items]
Shortfall payments billed and included in accounts receivable		$ 4.8
Period to utilize the current portion of shortfall payments to offset gathering fees to the extent that customer's throughput volumes exceed its MVC		7 years
Deferred tax liability, noncurrent		$ 1.2
General partner
Significant Accounting Policies [Line Items]
General partner interest (as a percent)	2.00%	2.00%

Represents the period to utilize the current portion of shortfall payments to offset gathering fees.

No definition available.

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- Definition

Represents the amount of shortfall payments billed to customers that was outstanding as of the reporting period date.

+ References

No definition available.

+ Details

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Namespace Prefix:	smlp_
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Period Type:	instant

- Details

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- Definition

Gross amount of noncurrent deferred tax liabilities, which result from applying the applicable tax rate to taxable temporary differences pertaining to each jurisdiction to which the entity is obligated to pay income tax.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=21917399&loc=d3e31917-109318

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319

+ Details

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Period Type:	instant

- Definition

Percentage investment held by the managing member or general partner of the limited liability company (LLC) or limited partnership (LP).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 272

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
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