Inventory (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Inventory [Line Items]
Carrying value of communities with impairment indicators	$ 34.2
Impairment charges	0.0	$ 4.2
Write-offs (recoveries) of earnest money deposits and pre-acquisition costs	$ 3.8	$ 3.8