Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Sep. 30, 2013	Mar. 31, 2015	Sep. 30, 2014
Business Information [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 993.4	$ 977.4	$ 697.7	$ 661.8
Homebuilding [Member]
Business Information [Line Items]
Earnest Money Deposits			64.4
Cash and Cash Equivalents, at Carrying Value			665.8	632.5
Homebuilding [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Business Information [Line Items]
Earnest Money Deposits			60.4	55.7
Cash and Cash Equivalents [Member]
Business Information [Line Items]
Prior Period Reclassification Adjustment	42.0	40.9
Subsidiaries [Member]
Business Information [Line Items]
Cash and Cash Equivalents, at Carrying Value			$ 40.5	$ 43.3