Capitalized Interest (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Rollforward of capitalized interest
Capitalized interest, beginning of period	$ 190.0	$ 215.0	$ 191.2	$ 208.0
Interest incurred	33.5	40.4	67.0	82.6
Interest charged to cost of sales	(37.3)	(40.9)	(72.0)	(76.1)
Capitalized interest, end of period	186.2	214.5	186.2	214.5
Financial Services and Other [Member]
Rollforward of capitalized interest
Interest incurred	$ 1.8	$ 1.9	$ 3.5	$ 3.5