Capitalized Interest (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Rollforward of capitalized interest
Capitalized interest, beginning of period	$ 255.1	$ 221.3	$ 237.4	$ 217.7
Interest incurred	50.6	36.7	96.8	73.6
Interest charged to cost of sales	(34.0)	(34.7)	(62.5)	(68.0)
Capitalized interest, end of period	271.7	223.3	271.7	223.3
Financial Services [Member]
Rollforward of capitalized interest
Interest incurred	9.7	3.0	17.8	7.0
Forestar Group [Member]
Rollforward of capitalized interest
Interest incurred	8.2	$ 8.1	16.4	$ 16.2
Rental
Rollforward of capitalized interest
Interest incurred	$ 13.7		$ 22.7

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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