Revenue - Schedule of Revenues Disaggregation by Product and Service Lines (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation Of Revenue [Line Items]
Revenues	$ 439.5	$ 414.2	$ 875.3	$ 824.1
Operating Segments | Network [Member]
Disaggregation Of Revenue [Line Items]
Revenues	247.0	241.0	490.5	483.8
Operating Segments | Network [Member] | Data [Member]
Disaggregation Of Revenue [Line Items]
Revenues	129.5	121.6	255.6	242.9
Operating Segments | Network [Member] | Video [Member]
Disaggregation Of Revenue [Line Items]
Revenues	48.4	47.9	97.0	96.5
Operating Segments | Network [Member] | Voice [Member]
Disaggregation Of Revenue [Line Items]
Revenues	57.7	64.6	117.0	130.5
Operating Segments | Network [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenues	11.4	6.9	20.9	13.9
Operating Segments | IT Services and Hardware [Member]
Disaggregation Of Revenue [Line Items]
Revenues	199.0	179.9	397.8	353.7
Operating Segments | IT Services and Hardware [Member] | Consulting
Disaggregation Of Revenue [Line Items]
Revenues	83.5	71.6	166.9	137.1
Operating Segments | IT Services and Hardware [Member] | Cloud
Disaggregation Of Revenue [Line Items]
Revenues	25.1	24.3	49.7	47.7
Operating Segments | IT Services and Hardware [Member] | Communications
Disaggregation Of Revenue [Line Items]
Revenues	54.3	55.0	109.2	109.0
Operating Segments | IT Services and Hardware [Member] | Infrastructure Solutions
Disaggregation Of Revenue [Line Items]
Revenues	36.1	29.0	72.0	59.9
Intersegment Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Revenues	(6.5)	(6.7)	(13.0)	(13.4)
Intersegment Eliminations [Member] | Network [Member]
Disaggregation Of Revenue [Line Items]
Revenues	4.8	4.9	9.7	9.7
Intersegment Eliminations [Member] | IT Services and Hardware [Member]
Disaggregation Of Revenue [Line Items]
Revenues	$ 1.7	$ 1.8	$ 3.3	$ 3.7