Revenues (Details) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022 USD ($) Lot	Mar. 31, 2021 USD ($) Lot	Mar. 31, 2022 USD ($) Lot	Mar. 31, 2021 USD ($) Lot	Sep. 30, 2021 USD ($)
Revenue from External Customer [Line Items]
Deferred development lot sales	$ 12.5	$ 0.0	$ 12.5	$ 0.0
Deferred income	6.8		6.8		$ 6.8
Tract sales and other	0.1	6.9	3.6	7.1
Revenues	$ 421.6	$ 287.1	$ 829.2	$ 594.2
Number of Lots Sold | Lot	5,788	3,588	10,304	7,155
Deferred Development Project
Revenue from External Customer [Line Items]
Residential lot sales	$ 54.7		$ 54.7
Number of Lots Sold | Lot	787		787
Proceeds from Deposits from Customers	$ 26.0
Real Estate [Member] | Residential Real Estate [Member]
Revenue from External Customer [Line Items]
Residential lot sales	409.0	$ 280.2	$ 813.1	$ 587.1
Revenues	$ 421.5	$ 280.2	$ 825.6	$ 587.1