Organization and Background (Details) $ in Thousands	9 Months Ended
Jun. 30, 2017 USD ($) state property property_unit investment	Sep. 30, 2016 USD ($)
Organization, background and significant accounting policies
Number of properties \| property	35
Number of units \| property_unit	9,890
Number of units in properties in lease up stage \| property_unit	445
Number of properties in lease up stage \| property	2
Number of units under construction \| property_unit	402
Number of states \| state	11
Real estate properties, net	$ 890,100	$ 759,576
Number of investments \| investment	2
Investments in unconsolidated joint ventures	$ 14,134	298
Real estate investments, other	16,182
Real estate loan	5,650	$ 19,500
Multi-family
Organization, background and significant accounting policies
Real estate properties, net	$ 901,084
Two Unconsolidated Joint Ventures
Organization, background and significant accounting policies
Number of investments \| investment	2
Investments in unconsolidated joint ventures	$ 13,925
Minimum \| Corporate Joint Venture \| Property Acquisition \| Multi-family
Organization, background and significant accounting policies
Equity contribution in each transaction (as a percent)	70.00%
Maximum \| Corporate Joint Venture \| Property Acquisition \| Multi-family
Organization, background and significant accounting policies
Equity contribution in each transaction (as a percent)	80.00%

Equity Method Investments, Number of Investments

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Number Of Real Estate Property In Lease Up Stage

+ References

No definition available.

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Number Of Units In Real Estate Property In Lease Up Stage

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Number of Units in Real Estate Property, Under Construction

+ References

No definition available.

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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 balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

+ 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(c))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

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

+ References

No definition available.

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

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No definition available.

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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

Amount of real estate owned for income production and capital accretion potential, not otherwise specified in the existing taxonomy. Such real estate excludes that which is occupied or used in the business, for entertainment purposes, or held in inventory for specific purposes.

+ 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.

+ Details

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- Definition

Percentage of subsidiary's or equity investee's stock owned by parent company after stock transaction.

+ References

No definition available.

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