Summary of Significant Accounting Policies - Intangible assets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Future amortization expense
2016	$ 24.8
2017	24.6
2018	24.1
2019	24.0
2020	23.5
Components of intangible assets and the related accumulated amortization
Cost	480.2	$ 507.7
Accumulated amortization	(144.8)	(127.4)
Total	$ 604.4	637.9
Minimum
Components of intangible assets and the related accumulated amortization
Intangible assets amortization period	3 years
Maximum
Components of intangible assets and the related accumulated amortization
Intangible assets amortization period	22 years
Trade names
Components of intangible assets and the related accumulated amortization
Trade names, indefinite lives	$ 124.2	130.2
Trade names
Components of intangible assets and the related accumulated amortization
Cost	0.2	6.1
Accumulated amortization	(0.1)	(5.9)
Customer relationships
Components of intangible assets and the related accumulated amortization
Cost	374.0	393.3
Accumulated amortization	(78.7)	(64.5)
Technology, including patents
Components of intangible assets and the related accumulated amortization
Cost	62.3	67.3
Accumulated amortization	(28.0)	(23.6)
Software
Components of intangible assets and the related accumulated amortization
Cost	43.3	40.4
Accumulated amortization	(37.7)	(33.0)
Other
Components of intangible assets and the related accumulated amortization
Cost	0.4	0.6
Accumulated amortization	$ (0.3)	$ (0.4)