Plant, Property and Equipment (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jul. 02, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Land and rights-of-way	$ 117,300,000		$ 117,300,000			$ 4,300,000
Buildings and leasehold improvements	304,300,000		304,300,000			179,100,000
Network equipment	3,849,300,000		3,849,300,000			3,339,400,000
Office software, furnitures, fixtures and vehicles	210,800,000		210,800,000			162,500,000
Construction in process	48,500,000		48,500,000			14,700,000
Gross value	4,530,200,000		4,530,200,000			3,700,000,000
Accumulated depreciation	(2,699,200,000)		(2,699,200,000)			(2,571,000,000)
Property, plant and equipment, net	1,831,000,000		1,831,000,000			1,129,000,000
Depreciation	71,700,000	$ 47,300,000	168,900,000	$ 140,000,000
Business Combinations, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment					$ 701,800,000
Depreciation associated with cost of providing services			0.82	0.85
Other Asset Impairment Charges	0	$ 0	0	$ 0
Capital Lease and Other Financing Arrangement Assets, Gross	$ 112,100,000		$ 112,100,000			$ 112,000,000