Capitalized Interest (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Mar. 31, 2014		Mar. 31, 2013
Rollforward of capitalized interest
Capitalized interest, beginning of period	$ 161.1		$ 91.3		$ 137.1		$ 82.3
Interest incurred	49.5	[1]	43.1	[1]	98.8	[1]	81.1	[1]
Interest expensed:
Directly to interest expense	0		(3.0)		0		(7.1)
Amortized to cost of sales	(26.9)		(27.6)		(52.2)		(52.5)
Capitalized interest, end of period	183.7		103.8		183.7		103.8
Financial Services [Member]
Rollforward of capitalized interest
Interest incurred	$ 0.9		$ 1.1		$ 1.8		$ 2.0

[1] Interest incurred includes interest incurred on the Company's financial services mortgage repurchase facility of $0.9 million and $1.8 million in the three and six months ended March 31, 2014, respectively, and $1.1 million and $2.0 million in the same periods of 2013.