Business Segment Information - Selected Financial Data for the Company's Business Segment Information (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues		$ 382.5	$ 386.7	$ 1,146.3	$ 979.2
Operating income		22.8	14.5	57.8	58.9
Expenditures for long-lived assets	[1]	56.7	283.7	167.3	357.5
Depreciation and amortization		75.5	75.5	229.1	177.6
Assets		2,619.0		2,619.0		$ 2,730.2
Operating Segments | Entertainment and Communications [Member]
Segment Reporting Information [Line Items]
Revenues		248.5	253.4	749.3	601.5
Operating income		27.7	25.0	81.2	79.1
Expenditures for long-lived assets	[1]	51.3	276.3	150.3	335.7
Depreciation and amortization		64.4	65.6	190.5	147.5
Assets		1,859.2		1,859.2		1,898.8
Operating Segments | IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Revenues		140.5	141.1	417.0	397.0
Operating income		0.6	7.3	(5.1)	8.5
Expenditures for long-lived assets	[1]	5.4	7.4	16.9	21.8
Depreciation and amortization		11.1	9.9	38.5	30.0
Assets		485.3		485.3		468.1
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues		(6.5)	(7.8)	(20.0)	(19.3)
Intersegment Elimination [Member] | Entertainment and Communications [Member]
Segment Reporting Information [Line Items]
Revenues		5.3	6.5	16.5	16.4
Intersegment Elimination [Member] | IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Revenues		1.2	1.3	3.5	2.9
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating income		(5.5)	(17.8)	(18.3)	(28.7)
Expenditures for long-lived assets	[1]	0.0	0.0	0.1	0.0
Depreciation and amortization		0.0	0.0	0.1	0.1
Corporate and Elimination [Member]
Segment Reporting Information [Line Items]
Assets		274.5		274.5		$ 363.3
Sales [Member] | Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues		$ 6.5	$ 7.8	$ 20.0	$ 19.3

[1] Includes cost of acquisitions