Business Segment Information - Selected Financial Data for the Company's Business Segment Information (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues		$ 384.2	$ 296.8	$ 763.8	$ 592.5
Operating income		24.9	20.2	35.0	44.4
Expenditures for long-lived assets	[1]	54.1	38.3	110.6	73.8
Depreciation and amortization		74.2	50.9	153.6	102.1
Assets		2,655.7		2,655.7		$ 2,730.2
Operating Segments | Entertainment and Communications [Member]
Segment Reporting Information [Line Items]
Revenues		250.5	173.9	500.8	348.1
Operating income		29.0	25.5	53.5	54.1
Expenditures for long-lived assets	[1]	47.9	31.8	99.0	59.4
Depreciation and amortization		63.4	41.0	126.1	81.9
Assets		1,886.4		1,886.4		1,898.8
Operating Segments | IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Revenues		140.2	128.3	276.5	255.9
Operating income		1.1	(0.2)	(5.7)	1.2
Expenditures for long-lived assets	[1]	6.1	6.5	11.5	14.4
Depreciation and amortization		10.7	9.9	27.4	20.1
Assets		480.0		480.0		468.1
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues		(6.5)	(5.4)	(13.5)	(11.5)
Intersegment Elimination [Member] | Entertainment and Communications [Member]
Segment Reporting Information [Line Items]
Revenues		5.2	4.7	11.2	9.9
Intersegment Elimination [Member] | IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Revenues		1.3	0.7	2.3	1.6
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating income		(5.2)	(5.1)	(12.8)	(10.9)
Expenditures for long-lived assets	[1]	0.1		0.1
Depreciation and amortization		0.1		0.1	0.1
Corporate and Elimination [Member]
Segment Reporting Information [Line Items]
Assets		289.3		289.3		$ 363.3
Sales [Member] | Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues		$ 6.5	$ 5.4	$ 13.5	$ 11.5

[1] Includes cost of acquisitions