Acquisitions and Dispositions - Schedule of Property Acquisitions (Details)														3 Months Ended		9 Months Ended
	Jun. 29, 2017 USD ($) property_unit	Jun. 02, 2017 USD ($) a property_unit	Apr. 04, 2017 USD ($) property_unit	Feb. 28, 2017 USD ($) property_unit	Nov. 04, 2016 USD ($) property_unit	May 31, 2016 USD ($) property_unit	May 11, 2016 USD ($) property_unit	May 06, 2016 USD ($) property_unit	Feb. 29, 2016 USD ($) property_unit	Feb. 01, 2016 USD ($) property_unit	Jan. 22, 2016 USD ($) property_unit	Nov. 18, 2015 USD ($) property_unit	Oct. 13, 2015 USD ($) a property_unit	Jun. 30, 2017 USD ($) property_unit	Jun. 30, 2016 USD ($) property_unit	Jun. 30, 2017 USD ($) property_unit	Jun. 30, 2016 USD ($) property_unit
Real Estate Properties
No. of Units | property_unit														9,890		9,890
Capitalized Acquisition Costs														$ 0	$ 1,408,000	$ 0	$ 2,418,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit														1,486	2,393	1,486	2,393
Purchase Price														$ 204,016,000	$ 205,350,000	$ 204,016,000	$ 205,350,000
Initial BRT Equity																47,131,000	49,006,000
Capitalized Acquisition Costs																2,761,000	2,418,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt														$ 140,300,000	$ 153,273,000	$ 140,300,000	$ 153,273,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Fredricksburg, VA | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit					220
Purchase Price					$ 38,490,000
Initial BRT Equity					$ 8,720,000
Ownership Percentage					80.00%
Capitalized Acquisition Costs					$ 643,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Fredricksburg, VA | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt					$ 29,900,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | St. Louis, MO | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit				53
Purchase Price				$ 8,000,000
Initial BRT Equity				$ 2,002,000
Ownership Percentage				75.50%
Capitalized Acquisition Costs				$ 134,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | St. Louis, MO | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt				$ 6,200,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | St. Louis, MO (Location 2) | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit				128
Purchase Price				$ 27,000,000
Initial BRT Equity				$ 6,001,000
Ownership Percentage				75.50%
Capitalized Acquisition Costs				$ 423,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | St. Louis, MO (Location 2) | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt				$ 20,000,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Creve Coeur, MO | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit			174
Purchase Price			$ 39,600,000
Initial BRT Equity			$ 9,408,000
Ownership Percentage			78.00%
Capitalized Acquisition Costs			$ 569,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Creve Coeur, MO | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt			$ 29,000,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | West Nashville, TN | Multi-family
Real Estate Properties
Area of land | a													41.5
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | West Nashville, TN | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit		402
Purchase Price		$ 5,228,000
Initial BRT Equity		$ 4,800,000
Ownership Percentage		58.00%
Capitalized Acquisition Costs		$ 0
Area of land | a		44.0
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | West Nashville, TN | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt		$ 0
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Farmers Branch, TX | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit	509
Purchase Price	$ 85,698,000
Initial BRT Equity	$ 16,200,000
Ownership Percentage	50.00%
Capitalized Acquisition Costs	$ 992,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Farmers Branch, TX | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt	$ 55,200,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | N. Charleston, SC | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit													271
Purchase Price													$ 3,625,000
Initial BRT Equity													$ 6,558,000
Ownership Percentage													65.00%
Capitalized Acquisition Costs													$ 0
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | N. Charleston, SC | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt													$ 0
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | La Grange, GA | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit												236
Purchase Price												$ 22,800,000
Initial BRT Equity												$ 6,824,000
Ownership Percentage												100.00%
Capitalized Acquisition Costs												$ 57,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | La Grange, GA | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt												$ 16,051,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Katy, TX | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit											268
Purchase Price											$ 40,250,000
Initial BRT Equity											$ 8,150,000
Ownership Percentage											75.00%
Capitalized Acquisition Costs											$ 382,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Katy, TX | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt											$ 30,750,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Macon, GA | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit										240
Purchase Price										$ 14,525,000
Initial BRT Equity										$ 3,250,000
Ownership Percentage										80.00%
Capitalized Acquisition Costs										$ 158,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Macon, GA | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt										$ 11,200,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Southaven, MS | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit									392
Purchase Price									$ 35,000,000
Initial BRT Equity									$ 5,856,000
Ownership Percentage									60.00%
Capitalized Acquisition Costs									$ 413,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Southaven, MS | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt									$ 28,000,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | San Antonio, TX | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit								288
Purchase Price								$ 35,150,000
Initial BRT Equity								$ 6,688,000
Ownership Percentage								65.00%
Capitalized Acquisition Costs								$ 539,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | San Antonio, TX | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt								$ 26,400,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Dallas, TX | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit							494
Purchase Price							$ 37,000,000
Initial BRT Equity							$ 6,750,000
Ownership Percentage							50.00%
Capitalized Acquisition Costs							$ 567,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Dallas, TX | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt							$ 27,938,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Columbia, SC | Multi-family | Property Acquisition
Real Estate Properties
No. of Units | property_unit						204
Purchase Price						$ 17,000,000
Initial BRT Equity						$ 4,930,000
Ownership Percentage						80.00%
Capitalized Acquisition Costs						$ 302,000
Corporate Joint Venture | Variable Interest Entity, Primary Beneficiary | Columbia, SC | Multi-family | Property Acquisition | Mortgages
Real Estate Properties
Acquisition Mortgage Debt						$ 12,934,000