PROPERTY AND EQUIPMENT (Schedule of Property and Equipment) (Details) - USD ($) $ in Millions	8 Months Ended	12 Months Ended
	Feb. 28, 2018	Jun. 30, 2019	Jun. 30, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross		$ 8,913.6	$ 8,054.2
Less accumulated depreciation		(3,104.7)	(2,590.9)
Less property and equipment held for sale			(35.7)
Property and equipment, net		5,808.9	5,427.6
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross		29.4	29.6
Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross		$ 372.9	321.8
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		45 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross		$ 49.1	61.7
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		$ 43.6	42.7
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		$ 82.0	70.1
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross		$ 699.4	585.1
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		$ 1,332.3	1,086.6
Circuit Switch Components and Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life in years		10 years
Property and equipment, gross		$ 407.1	399.4
Packet Switch Components and Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life in years		5 years
Property and equipment, gross		$ 68.6	58.1
Fiber Optic Network [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross		$ 5,307.2	4,933.6
Fiber Optic Network [Member] | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life in years	15 years	33 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		$ 522.0	$ 465.5