Homebuilding Interest (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Rollforward of capitalized homebuilding interest
Capitalized interest, beginning of period	$ 91.3	$ 79.8	$ 82.3	$ 79.2
Interest incurred	43.1	28.9	81.1	57.8
Interest expensed:
Directly to interest expense	(3.0)	(6.3)	(7.1)	(14.2)
Amortized to cost of sales	(27.6)	(21.3)	(52.5)	(41.7)
Capitalized interest, end of period	$ 103.8	$ 81.1	$ 103.8	$ 81.1