Capitalized Interest (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Rollforward of capitalized interest
Capitalized interest, beginning of period		$ 215.0	$ 205.2	$ 208.0	$ 198.5
Interest incurred	[1]	40.4	42.6	82.6	83.0
Interest expensed:
Charged to cost of sales		(40.9)	(35.6)	(76.1)	(69.2)
Written off with inventory impairments		0.0	0.0	0.0	(0.1)
Capitalized interest, end of period		214.5	212.2	214.5	212.2
Financial Services [Member]
Rollforward of capitalized interest
Interest incurred		$ 1.9	$ 1.6	$ 3.5	$ 3.1

[1] Interest incurred includes interest incurred on the Company's financial services mortgage repurchase facility of $1.9 million and $3.5 million in the three and six months ended March 31, 2016, respectively, and $1.6 million and $3.1 million in the same periods of 2015.