Basis of Presentation (Details) number in Millions, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)	Apr. 24, 2015 Lot Home	Sep. 30, 2014 USD ($)
Business Information [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 805.6	$ 617.3	$ 805.6	$ 617.3	$ 977.4		$ 661.8
Business Acquisition, Date of Acquisition Agreement	Apr. 24, 2015
Payments to Acquire Businesses, Net of Cash Acquired	$ 70.9		68.7	222.7
Payments for Previous Acquisition			2.0	$ 21.4
Business Acquisition, Number of Homes Acquired | Home						90
Business Acquisition, Number of Finished Lots | Lot						350
Business Acquisition, Number of Lots Under Option Contracts | Lot						400
Business Acquisition, Sales Order Backlog Acquired (Homes) | Home						42
Business Acquisition, Sales Order Backlog Acquired (Value)						18.7
Homebuilding [Member]
Business Information [Line Items]
Earnest Money Deposits	67.9		67.9
Cash and Cash Equivalents, at Carrying Value	766.7		766.7				632.5
Homebuilding [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Business Information [Line Items]
Earnest Money Deposits	64.2		64.2				55.7
Cash and Cash Equivalents [Member]
Business Information [Line Items]
Prior Period Reclassification Adjustment		$ 42.3			$ 40.9
Subsidiaries [Member]
Business Information [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 40.2		$ 40.2				$ 43.3