Inventory (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Inventory Impairments and Land Option Cost Write-Offs [Abstract]
Inventory Write-down	$ 0.0	$ 5.6	$ 1.7	$ 25.7
Write Offs Recoveries Of Earnest Money Deposits And Pre-Acquisition Costs		$ 23.0	$ 22.1	$ 28.3