Debt Obligations - Mortgage Payable (Details) - Mortgages - USD ($)	6 Months Ended
Mar. 31, 2018	Feb. 28, 2017
Debt Obligations
Acquisition Mortgage Debt	$ 131,707,000
Mortgages Maturing in January 2028 \| Madison, AL
Debt Obligations
Acquisition Mortgage Debt	$ 15,000,000
Interest rate	4.08%
Interest only period	60 months
Mortgages Maturing in January 2028 \| Boerne, TX
Debt Obligations
Acquisition Mortgage Debt	$ 9,200,000
Interest only period	36 months
Mortgages Maturing in January 2028 \| St. Louis, MO (Location 2)
Debt Obligations
Acquisition Mortgage Debt		$ 53,060,000
Interest rate		3.90%
Mortgages Maturing in March 2028 \| Lawrenceville, GA
Debt Obligations
Acquisition Mortgage Debt		$ 54,447,000
Interest rate		3.97%
London Interbank Offered Rate (LIBOR) \| Mortgages Maturing in January 2028 \| Boerne, TX
Debt Obligations
Basis spread on variable rate	2.39%
Maximum \| Mortgages Maturing in January 2028 \| Boerne, TX
Debt Obligations
Interest rate cap	3.86%

Debt Instrument, Interest Rate Cap

No definition available.

Name:	brt_DebtInstrumentInterestRateCap
Namespace Prefix:	brt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=brt_MortgagesMaturinginJanuary2028Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=brt_MadisonALMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=brt_BoerneTXMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=brt_St.LouisMOLocation2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=brt_MortgagesMaturinginMarch2028Member
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_StatementGeographicalAxis=brt_LawrencevilleGAMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
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Period Type: