Inventory (Details) - Homebuilding [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Inventory [Line Items]
Carrying value of communities with impairment indicators	$ 103.8		$ 103.8
Impairment charges	9.4	$ 3.2	9.4	$ 3.7
Write-offs (recoveries) of earnest money deposits and pre-acquisition costs	$ 2.8	$ 2.8	$ 5.1	$ 4.2