Accrued Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jun. 30, 2018
Accrued Liabilities, Current [Abstract]
Accrued compensation and benefits	$ 42.5	$ 83.3
Accrued postretirement benefits	15.4	15.4
Deferred revenue	12.5	10.4
Derivative financial instruments	4.0	0.0
Accrued interest expense	3.8	10.4
Accrued pension liabilities	3.3	3.3
Accrued income taxes	2.7	1.4
Other	23.3	24.4
Total accrued liabilities	$ 107.5	$ 148.6