Accrued Liabilities (Schedule of Accrued Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Jun. 30, 2016
Accrued Liabilities, Current [Abstract]
Accrued compensation and benefits	$ 38.5	$ 27.9
Accrued property and equipment purchases	81.8	46.7
Network expense accruals	132.1	94.8
Other accrued taxes	20.1	9.1
Accrued professional fees	3.9	2.3
Other accruals	49.0	44.9
Accrued Liabilities, Current, Total	$ 325.4	$ 225.7