Revenue - Schedule of Revenues Disaggregation by Product and Service Lines (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation Of Revenue [Line Items]
Revenues	$ 380.0	$ 379.6
Operating Segments [Member] | Entertainment and Communications [Member]
Disaggregation Of Revenue [Line Items]
Revenues	243.8	250.3
Operating Segments [Member] | IT Services and Hardware [Member]
Disaggregation Of Revenue [Line Items]
Revenues	142.3	136.3
Intersegment Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Revenues	(6.1)	(7.0)
Intersegment Eliminations [Member] | Entertainment and Communications [Member]
Disaggregation Of Revenue [Line Items]
Revenues	4.9	6.0
Intersegment Eliminations [Member] | IT Services and Hardware [Member]
Disaggregation Of Revenue [Line Items]
Revenues	1.2	1.0
Data [Member] | Operating Segments [Member] | Entertainment and Communications [Member]
Disaggregation Of Revenue [Line Items]
Revenues	119.3	117.5
Video [Member] | Operating Segments [Member] | Entertainment and Communications [Member]
Disaggregation Of Revenue [Line Items]
Revenues	48.7	51.7
Voice [Member] | Operating Segments [Member] | Entertainment and Communications [Member]
Disaggregation Of Revenue [Line Items]
Revenues	68.0	73.4
Other [Member] | Operating Segments [Member] | Entertainment and Communications [Member]
Disaggregation Of Revenue [Line Items]
Revenues	7.8	7.7
Consulting [Member] | Operating Segments [Member] | IT Services and Hardware [Member]
Disaggregation Of Revenue [Line Items]
Revenues	41.9	38.9
Cloud [Member] | Operating Segments [Member] | IT Services and Hardware [Member]
Disaggregation Of Revenue [Line Items]
Revenues	21.5	24.4
Communications [Member] | Operating Segments [Member] | IT Services and Hardware [Member]
Disaggregation Of Revenue [Line Items]
Revenues	51.2	47.4
Infrastructure Solutions [Member] | Operating Segments [Member] | IT Services and Hardware [Member]
Disaggregation Of Revenue [Line Items]
Revenues	$ 27.7	$ 25.6