Real Estate - Real Estate (Details) - USD ($)	3 Months Ended
Dec. 31, 2018	Sep. 30, 2018
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Payments to Acquire Residential Real Estate	$ 163,500,000
Payments to Develop Real Estate Assets	57,300,000
Real estate	693,200,000	$ 498,000,000
Developed and under development projects
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Real estate	644,700,000	463,100,000
Land [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Real estate	$ 48,500,000	$ 34,900,000
Minimum [Member] \| D.R. Horton, Inc. [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Notes Receivable, Related Parties	12.00%
Maximum [Member] \| D.R. Horton, Inc. [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Notes Receivable, Related Parties	16.00%

The interest rate for investments that have an interest rate. For fixed rate investments, this indicates the fixed interest rate. If the investment has a variable interest rate, the rate stated here may be the rate that is currently relevant. In this case the "Investment, Interest Rate is Current Rate for Variable Rate Investment Flag", "Investment, Interest Rate is Discount Rate at Purchase Flag", "Investment, Interest Rate Reflects Current Yield Flag" should be used. If one of these flags are not appropriate to explain the interest rate that is indicated, then a new flag should be added or an explanation should be included in "Investment, Additional Information".

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Sentence Column A

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- Definition

Carrying amount as of the balance sheet date, net of valuation allowances and impairment losses, of costs of land expected to be developed in the near term plus capitalized costs of development, for purposes of selling completed units to home buyers or commercial or industrial entities..

+ 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 210.5-02.6(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

The cash outflow from the acquisition of residential property intended to generate income for the owner.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

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- Definition

Payments to develop real estate assets is the process of adding improvements on or to a parcel of land. Such improvements may include drainage, utilities, subdividing, access, buildings, and any combination of these elements; and are generally classified as cash flow from investing activities.

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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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