Inventory Impairments and Land Option Cost Write-Offs (Details) (Homebuilding [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Homebuilding [Member]
Inventory Impairments and Land Option Cost Write Offs [Abstract]
Carrying value of communities with impairment indicators	$ 424.2		$ 424.2
Impairment charges	8.1	2.3	12.0	2.3
Write-offs (recoveries) of earnest money deposits and pre-acquisition costs	$ 4.4	$ 2.1	$ 6.6	$ 4.8