ACQUISITIONS, DISPOSITIONS AND IMPAIRMENT CHARGES - Schedule of Property Dispositions (Details)															12 Months Ended
	Oct. 25, 2017 USD ($) property_unit	Jul. 27, 2017 USD ($) property_unit	Dec. 21, 2016 USD ($) property_unit	Dec. 17, 2016 USD ($) property_unit	Nov. 30, 2016 USD ($) property_unit	Nov. 21, 2016 USD ($) property_unit	Oct. 26, 2016 USD ($) property_unit	Oct. 19, 2016 USD ($) property_unit	Sep. 01, 2016 USD ($) property_unit	Jun. 06, 2016 USD ($) property_unit	Jun. 01, 2016 USD ($) property_unit	Apr. 06, 2016 USD ($) property_unit	Mar. 15, 2016 USD ($) property_unit	Mar. 02, 2016 USD ($) property_unit	Sep. 30, 2017 USD ($) property_unit	Sep. 30, 2016 USD ($) property_unit	Sep. 30, 2015 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit															9,568
Gain on Sale															$ 0	$ (2,788,000)	$ (6,329,000)
Impairment of real estate															$ 0	$ 0	$ 0
Disposition of real estate properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit															1,581	2,208
Sales Price															$ 169,760,000	$ 202,049,000
Gain on Sale															52,601,000	46,864,000
Non-controlling partner portion of gain															$ 24,840,000	$ 18,795,000
Disposition of real estate properties | Greenville, NC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit								350
Sales Price								$ 68,000,000
Gain on Sale								18,483,000
Non-controlling partner portion of gain								$ 9,329,000
Disposition of real estate properties | Panama City, FL
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit							160
Sales Price							$ 14,720,000
Gain on Sale							7,393,000
Non-controlling partner portion of gain							$ 3,478,000
Disposition of real estate properties | Atlanta, GA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit						350
Sales Price						$ 36,750,000
Gain on Sale						8,905,000
Non-controlling partner portion of gain						$ 4,166,000
Disposition of real estate properties | Hixson, TN
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit					156
Sales Price					$ 10,775,000
Gain on Sale					608,000
Non-controlling partner portion of gain					$ 152,000
Disposition of real estate properties | New York, NY (Location 1)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit			1
Sales Price			$ 465,000
Gain on Sale			449,000
Non-controlling partner portion of gain			$ 0
Disposition of real estate properties | Humble, TX (Parkside)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit		260
Sales Price		$ 18,000,000
Gain on Sale		7,707,000
Non-controlling partner portion of gain		$ 3,143,000
Disposition of real estate properties | Humble, TX (Meadowbrook)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit		160
Sales Price		$ 11,300,000
Gain on Sale		4,767,000
Non-controlling partner portion of gain		$ 1,943,000
Disposition of real estate properties | Pasadena, TX
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit		144
Sales Price		$ 9,750,000
Gain on Sale		4,289,000
Non-controlling partner portion of gain		$ 2,629,000
Disposition of real estate properties | Cordova, TN
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit														464
Sales Price														$ 31,100,000
Gain on Sale														6,731,000
Non-controlling partner portion of gain														$ 2,195,000
Disposition of real estate properties | Kennesaw, GA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit													450
Sales Price													$ 64,000,000
Gain on Sale													17,462,000
Non-controlling partner portion of gain													$ 10,037,000
Disposition of real estate properties | Pooler, GA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit												300
Sales Price												$ 38,500,000
Gain on Sale												5,710,000
Non-controlling partner portion of gain												$ 1,405,000
Disposition of real estate properties | Collierville, TN
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit											324
Sales Price											$ 34,300,000
Gain on Sale											4,586,000
Non-controlling partner portion of gain											$ 917,000
Disposition of real estate properties | Little Rock, AK
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit										172
Sales Price										$ 2,372,000
Gain on Sale										386,000
Non-controlling partner portion of gain										$ 0
Disposition of real estate properties | Wichita, KS
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit									496
Sales Price									$ 30,400,000
Gain on Sale									10,718,000
Non-controlling partner portion of gain									$ 4,241,000
Disposition of real estate properties | New York, NY (Location 2)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit				2
Sales Price				$ 1,377,000
Gain on Sale				1,271,000
Non-controlling partner portion of gain				$ 0
Subsequent event | Disposition of real estate properties | Melbourne, FL
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
No. of Units | property_unit	208
Sales Price	$ 22,250,000
Gain on Sale	12,700,000
Non-controlling partner portion of gain	$ 2,800,000