Inventory (Details) - Homebuilding [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Inventory Impairments Information [Line Items]
Carrying value of communities with impairment indicators	$ 160.9	$ 160.9
Impairment charges	$ 11.4	20.3	$ 44.9	$ 75.2
Write-offs (recoveries) of earnest money deposits and pre-acquisition costs		$ 11.1	$ 15.4	$ 10.0