Property and Equipment (Schedule of Property and Equipment) (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Property, Plant and Equipment [Line Items]
Estimated useful life in years	8 years
Property and equipment, gross	$ 6,962.5	$ 5,499.6
Less accumulated depreciation	(1,946.5)	(1,420.1)
Property, Plant and Equipment, Net, Total	5,016.0	4,079.5
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	28.9	16.7
Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 277.1	187.3
Building Improvements [Member] | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life in years	15 years
Building Improvements [Member] | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life in years	39 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 27.3	6.8
Furniture and Fixtures [Member] | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life in years	3 years
Furniture and Fixtures [Member] | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life in years	7 years
Computer Hardware [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 33.1	24.5
Computer Hardware [Member] | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life in years	3 years
Computer Hardware [Member] | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life in years	5 years
Software [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life in years	3 years
Property and equipment, gross	$ 56.5	37.2
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 483.4	326.6
Machinery and Equipment [Member] | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life in years	5 years
Machinery and Equipment [Member] | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life in years	7 years
Fiber Optic Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life in years	8 years
Property and equipment, gross	$ 826.6	732.5
Circuit Switch Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life in years	10 years
Property and equipment, gross	$ 337.6	20.3
Packet Switch Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life in years	5 years
Property and equipment, gross	$ 130.2	97.9
Fiber Optic Network [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 4,110.3	3,393.0
Fiber Optic Network [Member] | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life in years	15 years
Fiber Optic Network [Member] | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life in years	20 years
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 651.5	$ 656.8