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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenue	$ 380.0	$ 384.2	$ 760.0	$ 763.8
Operating income (loss)	27.7	24.9	7.5	35.0
Expenditures for long-lived assets	48.5	54.1	99.4	110.6
Depreciation and amortization	74.7	74.2	148.9	153.6
Assets	2,594.2		2,594.2		$ 2,653.8
Operating Segments [Member] | Entertainment and Communications [Member]
Segment Reporting Information [Line Items]
Revenue	239.7	250.5	483.5	500.8
Operating income (loss)	30.5	29.0	42.6	53.5
Expenditures for long-lived assets	42.2	47.9	86.6	99.0
Depreciation and amortization	64.5	63.4	128.4	126.1
Assets	1,801.5		1,801.5		1,840.0
Operating Segments [Member] | IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Revenue	147.0	140.2	289.3	276.5
Operating income (loss)	5.2	1.1	6.9	(5.7)
Expenditures for long-lived assets	6.3	6.1	12.8	11.5
Depreciation and amortization	10.2	10.7	20.5	27.4
Assets	452.3		452.3		500.7
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenue	(6.7)	(6.5)	(12.8)	(13.5)
Intersegment Elimination [Member] | Entertainment and Communications [Member]
Segment Reporting Information [Line Items]
Revenue	5.0	5.2	9.9	11.2
Intersegment Elimination [Member] | IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Revenue	1.7	1.3	2.9	2.3
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	(8.0)	(5.2)	(42.0)	(12.8)
Expenditures for long-lived assets	0.0	0.1	0.0	0.1
Depreciation and amortization	0.0	0.1	0.0	0.1
Corporate and Elimination [Member]
Segment Reporting Information [Line Items]
Assets	340.4		340.4		$ 313.1
Sales [Member] | Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenue	$ 6.7	$ 6.5	$ 12.8	$ 13.5