Spin Costs (Restructuring and Related Costs) (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Total					$ 0.0	$ (2.5)	$ 4.9
Spin-off
Restructuring Cost and Reserve [Line Items]
Severance and termination related costs							0.2
Non-cash asset write-down							0.5
Contract termination costs						(2.5)	3.7
Other exit costs							2.0
Net gain on asset sale						(1.3)	(0.6)
Total	$ 0.0	$ 0.0	$ (1.4)	$ (1.0)	$ 0.0	(3.8)	5.8
Corporate | Spin-off
Restructuring Cost and Reserve [Line Items]
Severance and termination related costs							0.5
Non-cash asset write-down							0.0
Contract termination costs						(2.5)	0.0
Other exit costs							0.0
Net gain on asset sale						0.0	0.0
Total						(2.5)	0.5
Americas | Segments | Spin-off
Restructuring Cost and Reserve [Line Items]
Severance and termination related costs							(2.2)
Non-cash asset write-down							0.0
Contract termination costs						0.0	3.7
Other exit costs							0.3
Net gain on asset sale						(1.3)	0.0
Total						(1.3)	1.8
International | Segments | Spin-off
Restructuring Cost and Reserve [Line Items]
Severance and termination related costs							1.9
Non-cash asset write-down							0.5
Contract termination costs						0.0	0.0
Other exit costs							1.7
Net gain on asset sale						0.0	(0.6)
Total						$ 0.0	$ 3.5