Summary of Significant Accounting Policies (Guarantees) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Accounting Policies [Abstract]
Warranty term, generally	1 year
Guarantees
Balance at October 1	$ 27.5	$ 32.1	$ 28.4
Provision for warranties during the period	13.9	13.9	14.7
Warranty reserves acquired	1.5	2.6	7.1
Warranty claims incurred during the period	(17.4)	(21.1)	(18.1)
Balance at September 30	$ 25.5	$ 27.5	$ 32.1