Real Estate - Text (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2018	Sep. 30, 2020	Sep. 30, 2019
Real Estate Properties [Line Items]
Payments to Acquire Residential Real Estate		$ 550.8
Payments to Develop Real Estate Assets		503.0
Inventory Write-down	$ 0.3	0.0	$ 0.8
Due Diligence Write-Offs		$ 0.9	$ 0.2
D.R. Horton, Inc. [Member]
Real Estate Properties [Line Items]
Related Party Transaction, Rate		16.00%

Due Diligence Write-Offs

No definition available.

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- Definition

Amount of loss from reductions in inventory due to subsequent measurement adjustments, including, but not limited to, physical deterioration, obsolescence, or changes in price levels.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=116847112&loc=d3e4542-108314

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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3213-108585

+ Details

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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.

+ References

+ Details

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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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- Definition

Identify the stated interest rate per the agreement, for example, leasing and debt arrangements between related parties.

+ References

No definition available.

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