Organization and Background - Narrative (Details) $ in Thousands	Jun. 30, 2018 USD ($) property_Unit state property investment	Sep. 30, 2017 USD ($)
Organization, background and significant accounting policies
Number of properties \| property	36
Number of units \| property_Unit	10,121
Number of units under construction \| property_Unit	402
Number of states \| state	11
Real estate properties, net	$ 1,054,484	$ 902,281
Investments in unconsolidated joint ventures	20,542	$ 21,415
Multi-family
Organization, background and significant accounting policies
Real estate properties, net	$ 1,044,063
Unconsolidated joint ventures
Organization, background and significant accounting policies
Number of properties \| property	1,026
Number of investments \| investment	3
Investments in unconsolidated joint ventures	$ 20,328

Equity Method Investments, Number of Investments

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- Definition

Number of Units in Real Estate Property, Under Construction

+ References

No definition available.

+ Details

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- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

The number of states the entity operates in as of the balance sheet date.

+ References

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- Definition

The number of units in a real estate property owned as of the balance sheet date.

+ References

No definition available.

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- Definition

Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(d))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- 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.

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