Accrued Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Jun. 30, 2017
Accrued Liabilities, Current [Abstract]
Accrued compensation and benefits	$ 52.6	$ 59.1
Accrued postretirement benefits	15.5	15.5
Accrued interest expense	11.2	11.2
Deferred revenue	10.7	9.8
Derivative financial instruments	2.9	13.1
Other	25.5	31.2
Total accrued liabilities	$ 118.4	$ 139.9