Spin Costs - Schedule of Restructuring Reserve by Type of Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Restructuring Reserve [Roll Forward]
Restructuring	$ 0.0	$ 3.1
Severance & Termination Related Costs
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	2.8	12.0
Restructuring	0.0	0.3
Other	0.0	(0.2)
Cash	(1.8)	(6.5)
Non-Cash	0.0	0.0
Restructuring Reserve, Ending Balance	1.0	5.6
Contract termination costs
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	3.6
Restructuring	0.0
Other	0.0
Cash	(0.3)
Non-Cash	0.0
Restructuring Reserve, Ending Balance	3.3
Net (gain)/loss on asset sales
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	0.0
Restructuring	(1.3)
Other	0.0
Cash	1.3
Non-Cash	0.0
Restructuring Reserve, Ending Balance	0.0
Other exit costs
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance		0.3
Restructuring		0.6
Other		0.0
Cash		(0.7)
Non-Cash		0.0
Restructuring Reserve, Ending Balance		0.2
Spin-off
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	6.4	12.3
Restructuring	(1.3)	0.9
Other	0.0	(0.2)
Cash	(0.8)	(7.2)
Non-Cash	0.0	0.0
Restructuring Reserve, Ending Balance	$ 4.3	$ 5.8