Capitalized Interest Capitalized Interest (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Real Estate Inventory, Capitalized Interest Costs [Roll Forward]
Capitalized interest, beginning of year	$ 237.4	$ 217.7	$ 207.7
Interest incurred	203.5	162.5	152.2
Charged to cost of sales	(154.5)	(142.8)	(142.2)
Capitalized interest, end of year	286.4	237.4	217.7
Financial Services [Member]
Real Estate Inventory, Capitalized Interest Costs [Roll Forward]
Interest incurred	45.9	18.9	17.0
Forestar Group [Member]
Real Estate Inventory, Capitalized Interest Costs [Roll Forward]
Interest incurred	32.8	$ 32.9	$ 41.6
Rental
Real Estate Inventory, Capitalized Interest Costs [Roll Forward]
Interest incurred	$ 56.0

Total interest costs incurred during the period and either capitalized or charged against earnings.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483013/835-20-50-1

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- Definition

Carrying amount as of the balance sheet date of interest costs that were capitalized to properties under development during the land development and construction period of a project, and which are included in inventory.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 835
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483013/835-20-50-1

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- Definition

Amount of interest cost charged to cost of sales that had been previously capitalized to inventory.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-SubTopic 20
-Topic 835
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483013/835-20-50-1

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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