Mortgage Notes Payable - Summary (Details) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2020 USD ($) item	Dec. 31, 2019 USD ($) loan item Lender
MORTGAGE NOTES PAYABLE
Long-term debt, gross	$ 405,001
Residential Property \| Mortgage Notes Payable
MORTGAGE NOTES PAYABLE
Number of mortgage loans out of compliance \| loan		10
Outstanding balance of loans out of compliance, in aggregate		$ 16,361
Outstanding balance of mortgage loans out of compliance in which annual waivers were received from the lenders		$ 10,435
Number of lenders in which annual waivers were not received for loans out of compliance \| Lender		1
Outstanding balance of mortgage loans out of compliance in which annual waivers were not received from the lender		$ 5,926
Fixed rate mortgage notes payable \| Mortgage Notes Payable
MORTGAGE NOTES PAYABLE
Long-term debt, gross	405,001	395,038
Less unamortized debt issuance costs	1,833	1,874
Long-term debt, net	403,168	393,164
Debt swapped from variable to fixed rate	$ 26,205	$ 12,960
Number of mortgage loans \| item	122	121
Fixed rate mortgage notes payable \| Mortgage Notes Payable \| Minimum
MORTGAGE NOTES PAYABLE
Effective interest rate (as a percent)	2.43%	3.15%
Fixed rate mortgage notes payable \| Mortgage Notes Payable \| Maximum
MORTGAGE NOTES PAYABLE
Effective interest rate (as a percent)	6.85%	7.25%
Fixed rate mortgage notes payable \| Mortgage Notes Payable \| Weighted Average
MORTGAGE NOTES PAYABLE
Effective interest rate (as a percent)	4.18%	4.31%

The number of lenders in which annual waivers were not received for loans out of compliance.

No definition available.

Name:	sret_AnnualWaiversNotReceivedFromLendersNumberOfLenders
Namespace Prefix:	sret_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the amount of mortgage debt swapped from variable rate to fixed rate.

+ References

No definition available.

+ Details

Name:	sret_DebtSwappedFromVariableRateToFixedRate
Namespace Prefix:	sret_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The outstanding balance of mortgage loans out of compliance in which annual waivers were not received from the lenders.

+ References

No definition available.

+ Details

Name:	sret_MortgageLoansOutOfComplianceWaiversNotReceivedFromLendersOutstandingBalance
Namespace Prefix:	sret_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The outstanding balance of mortgage loans out of compliance in which annual waivers were received from the lenders.

+ References

No definition available.

+ Details

Name:	sret_MortgageLoansOutOfComplianceWaiversReceivedFromLendersOutstandingBalance
Namespace Prefix:	sret_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the number of mortgage notes payable out of compliance.

+ References

No definition available.

+ Details

Name:	sret_MortgageNotesPayableNumberOfLoansOutOfCompliance
Namespace Prefix:	sret_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The principal amount outstanding, in aggregate, of the mortgage notes payable that are out of compliance as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	sret_MortgageNotesPayablePrincipalAmountOfLoanOutOfComplianceAggregateAmount
Namespace Prefix:	sret_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the number of mortgage loans.

+ References

No definition available.

+ Details

Name:	sret_NumberOfMortgageLoans
Namespace Prefix:	sret_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	srt_MortgageLoansOnRealEstateLineItems
Namespace Prefix:	srt_
Data Type:	xbrli:stringItemType
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: 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(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-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

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28555-108399

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: 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(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=us-gaap_ResidentialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=sret_MortgageNotesPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=sret_FixedRateMortgageNotesPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: