Spin Costs - Schedule of Restructuring Reserve by Type of Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance		$ 6.4
Spin restructuring	$ 0.0	(1.3)
Cash		(0.8)
Non-Cash		0.0
Restructuring Reserve, Ending Balance		4.3
Severance and termination related costs
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance		2.8
Spin restructuring		0.0
Cash		(1.8)
Non-Cash		0.0
Restructuring Reserve, Ending Balance		1.0
Contract termination costs
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance		3.6
Spin restructuring		0.0
Cash		(0.3)
Non-Cash		0.0
Restructuring Reserve, Ending Balance		3.3
Net gain on asset sales
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance		0.0
Spin restructuring		(1.3)
Cash		1.3
Non-Cash		0.0
Restructuring Reserve, Ending Balance		$ 0.0