Inventory (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Inventory [Line Items]
Carrying value of communities with impairment indicators	$ 59.8
Impairment charges	4.2	$ 1.4
Write-offs (recoveries) of earnest money deposits and pre-acquisition costs	$ 3.8	$ 2.3