Inventory (Details) - Homebuilding [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Inventory [Line Items]
Carrying value of communities with impairment indicators	$ 216.5		$ 216.5
Impairment charges	3.2	$ 8.1	3.7	$ 12.0
Write-offs (recoveries) of earnest money deposits and pre-acquisition costs	$ 2.8	$ 4.4	$ 4.2	$ 6.6