Business Segment Information (Details)		3 Months Ended									12 Months Ended
		Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Goodwill, Impairment Loss											$ 0	$ 0
Segment Reporting [Abstract]
Revenue		$ 427,100,000	$ 289,200,000	$ 294,000,000	$ 278,200,000	$ 285,300,000	$ 312,400,000	$ 299,200,000	$ 288,900,000		1,288,500,000	1,185,800,000	$ 1,167,800,000
Operating (loss) income		9,800,000	$ 12,700,000	20,900,000	(5,300,000)	10,500,000	$ 25,500,000	$ 27,400,000	$ 29,600,000		38,100,000	93,000,000	128,000,000
Payments to Acquire Property, Plant, and Equipment											210,500,000	286,400,000	283,600,000
Depreciation and amortization											193,000,000	182,200,000	141,600,000
Assets		2,162,400,000				1,541,000,000					2,162,400,000	1,541,000,000
Service revenue											1,006,100,000	978,700,000	933,000,000
Product revenue											$ 282,400,000	$ 207,100,000	$ 234,800,000
Segment Reporting [Abstract]
Number of Operating Segments											2	2	2
Restructuring and severance related charges		3,500,000		$ 3,600,000	25,600,000	11,900,000					$ 32,700,000	$ 11,900,000	$ 6,000,000
Impairment of assets, excluding goodwill											0	0	0
Revenue Contributed from Acquired Companies											172,800,000
Increases (Decreases) in Total Assets											621,400,000
Restricted Cash, Current		378,700,000				0					378,700,000	0
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent		19,300,000				64,500,000					19,300,000	64,500,000
Deferred Tax Liabilities, Net, Noncurrent		11,200,000				0					11,200,000	0
Handsets and accessories [Member]
Segment Reporting [Abstract]
Product revenue											3,100,000	4,500,000	7,400,000
IT, telephony and other equipment [Member]
Segment Reporting [Abstract]
Product revenue											279,300,000	202,600,000	227,400,000
Entertainment and Communications [Member]
Segment Reporting [Abstract]
Revenue											789,900,000	768,800,000	743,700,000
Operating (loss) income											65,300,000	90,600,000	129,900,000
Payments to Acquire Property, Plant, and Equipment											196,400,000	272,500,000	269,500,000
Depreciation and amortization											174,700,000	168,600,000	129,200,000
Assets		1,117,800,000				1,093,500,000					1,117,800,000	1,093,500,000
Service revenue											785,100,000	763,000,000	735,000,000
Segment Reporting [Abstract]
Restructuring and severance related charges											27,900,000	7,700,000	1,600,000
Impairment of assets, excluding goodwill					$ 0					$ 0		0
IT Services and Hardware [Member]
Segment Reporting [Abstract]
Revenue											511,800,000	430,700,000	435,400,000
Operating (loss) income											10,600,000	23,200,000	20,600,000
Payments to Acquire Property, Plant, and Equipment												13,700,000	14,000,000
Depreciation and amortization											18,100,000	13,500,000	12,300,000
Assets		444,000,000				60,000,000					444,000,000	60,000,000
Service revenue											221,000,000	215,700,000	198,000,000
Segment Reporting [Abstract]
Restructuring and severance related charges											4,800,000	3,300,000	2,800,000
Impairment of assets, excluding goodwill											4,700,000
Increase (decrease) in Revenue											81,100,000	4,700,000
Increases (Decreases) in Total Assets											384,000,000
Corporate Segment [Member]
Segment Reporting [Abstract]
Operating (loss) income											(37,800,000)	(20,800,000)	(22,500,000)
Payments to Acquire Property, Plant, and Equipment											0	200,000	100,000
Depreciation and amortization											200,000	100,000	100,000
Segment Reporting [Abstract]
Restructuring and severance related charges											0	900,000	1,600,000
Increases (Decreases) in Total Assets											213,100,000
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent		19,300,000				64,500,000					19,300,000	64,500,000
Deferred Tax Liabilities, Net, Noncurrent		11,200,000									11,200,000
Intersegment Eliminations [Member]
Segment Reporting [Abstract]
Revenue											(13,200,000)	(13,700,000)	(11,300,000)
Intersegment Eliminations [Member] | Entertainment and Communications [Member]
Segment Reporting [Abstract]
Revenue											1,700,000	1,300,000	1,300,000
Intersegment Eliminations [Member] | IT Services and Hardware [Member]
Segment Reporting [Abstract]
Revenue											11,500,000	12,400,000	10,000,000
Intersegment Eliminations [Member] | Corporate Segment [Member]
Segment Reporting [Abstract]
Assets		$ 600,600,000				$ 387,500,000					600,600,000	387,500,000
Sales [Member] | Intersegment Eliminations [Member]
Segment Reporting [Abstract]
Revenue											13,200,000	13,700,000	11,300,000
Professional Services [Member]
Segment Reporting [Abstract]
Revenue Contributed from Acquired Companies											29,600,000
Telecom and IT equipment [Member]
Segment Reporting [Abstract]
Revenue Contributed from Acquired Companies											132,700,000
Telecom and IT equipment [Member] | IT Services and Hardware [Member]
Segment Reporting [Abstract]
Increase (decrease) in Revenue												24,500,000
Cloud [Member]
Segment Reporting [Abstract]
Revenue Contributed from Acquired Companies											6,800,000
Managed and Professional Services [Member] | IT Services and Hardware [Member]
Segment Reporting [Abstract]
Increase (decrease) in Revenue												17,700,000
Continuing Operations [Member]
Segment Reporting [Abstract]
Payments to Acquire Property, Plant, and Equipment												286,400,000	283,600,000
Depreciation and amortization											193,000,000	$ 182,200,000	$ 141,600,000
Expenditures for Long-Lived Assets, Including Acquisitions of Businesses [Member] | IT Services and Hardware [Member]
Segment Reporting [Abstract]
Payments to Acquire Property, Plant, and Equipment	[1]										181,100,000
Expenditures for Long-Lived Assets, Including Acquisitions of Businesses [Member] | Continuing Operations [Member]
Segment Reporting [Abstract]
Payments to Acquire Property, Plant, and Equipment	[1]										$ 377,500,000

[1] Includes cost of acquisitions