Partners' Capital (EPU) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Partners' Capital
Weighted Average Units Outstanding, Common Units - Basic and Diluted (in units)	14,738,528	13,400,138
Assumed net loss to be allocated	$ (7,839)	$ (17,688)
Basic and diluted loss per unit (in dollars per share)	$ (0.53)	$ (1.32)
Asset impairments		$ 4,688

Per unit of ownership amount after tax of income (loss), basic and diluted, available to outstanding limited partnership (LP) unit-holder.

No definition available.

+ Details

Name:	snmp_NetIncomeLossPerOutstandingLimitedPartnershipUnitBasicAndDilutedNetOfTax
Namespace Prefix:	snmp_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The average number of limited partnership units issued and outstanding that are used in calculating basic and diluted earnings per limited partnership and general partnership unit.

+ References

No definition available.

+ Details

Name:	snmp_WeightedAverageNumberOfLimitedPartnershipUnitOutstandingBasicAndDiluted
Namespace Prefix:	snmp_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2420-110228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=96947427&loc=d3e1377-109256

+ Details

Name:	us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration