Loan receivable weighted average maturity.

No definition available.

Name:	smta_LoanReceivableWeightedAverageMaturity
Namespace Prefix:	smta_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of real estate properties mortgage loans receivables secured by.

+ References

No definition available.

+ Details

Name:	smta_NumberOfRealEstatePropertiesMortgageLoansReceivablesSecuredBy
Namespace Prefix:	smta_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Related party transaction number of mortgage loans receivables.

+ References

No definition available.

+ Details

Name:	smta_RelatedPartyTransactionNumberOfMortgageLoansReceivables
Namespace Prefix:	smta_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Interest rate of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Paragraph Column B
-Subsection 29

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column B))
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

+ Details

Name:	srt_MortgageLoansOnRealEstateInterestRate
Namespace Prefix:	srt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of interest income earned from interest-bearing assets owed to the entity by related party.

+ References

No definition available.

+ Details

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

- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LoansAndLeasesReceivableNetReportedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

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

- Details

Name:	srt_CounterpartyNameAxis=smta_SpiritRealtyCapitalIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_AffiliatedEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=smta_RelatedPartyMortgageLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Related Party Transactions - Related Party Loans Receivable (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) property loan	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) property loan	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Related Party Transaction [Line Items]
Loans receivable, net	$ 26,405		$ 26,405		$ 30,093
Spirit Realty Capital, Inc. \| Affiliated entity
Related Party Transaction [Line Items]
Number of mortgage loans receivables borrowed by subsidiaries \| loan	4		4
Spirit Realty Capital, Inc. \| Related Party Mortgage Loans \| Affiliated entity
Related Party Transaction [Line Items]
Number of real estate properties, mortgage loans receivables secured by \| property	6		6
Loans receivable, interest rate			1.00%
Loans receivable, net	$ 26,400		$ 26,400		$ 27,900
Interest income, related party	$ 67	$ 74	$ 135	$ 150
Weighted average maturity on loan receivable			8 years 8 months 12 days