Inventory Impairments and Land Option Cost Write-Offs (Details) - Homebuilding [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Inventory Impairments Information [Line Items]
Carrying value of communities with impairment indicators	$ 328.7	$ 328.7
Impairment charges	21.2	44.9	$ 75.2	$ 21.3
Write-offs (recoveries) of earnest money deposits and pre-acquisition costs		15.4	10.0	9.8
West [Member]
Inventory Impairments Information [Line Items]
Impairment charges	9.0	20.4	5.1	20.2
Midwest [Member]
Inventory Impairments Information [Line Items]
Impairment charges		0.0	49.3	0.0
East [Member]
Inventory Impairments Information [Line Items]
Impairment charges	$ 6.0	$ 14.3	$ 17.7	$ 0.1