Revenue - Schedule of Revenues Disaggregation by Contract Type (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation Of Revenue [Line Items]
Revenues	$ 389.5	$ 382.5	$ 1,149.5	$ 1,146.3
Intersegment Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Revenues	(6.7)	(6.5)	(19.5)	(20.0)
Transferred at Point in Time [Member]
Disaggregation Of Revenue [Line Items]
Revenues	40.7	41.2	112.3	118.8
Transferred at Point in Time [Member] | Intersegment Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Revenues	0.0	0.0	0.0	0.0
Transferred over Time [Member]
Disaggregation Of Revenue [Line Items]
Revenues	348.8	341.3	1,037.2	1,027.5
Transferred over Time [Member] | Intersegment Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Revenues	0.0	0.0	0.0	0.0
Entertainment and Communications [Member] | Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenues	241.0	248.5	724.5	749.3
Entertainment and Communications [Member] | Intersegment Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Revenues	4.9	5.3	14.8	16.5
Entertainment and Communications [Member] | Transferred at Point in Time [Member] | Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenues	6.6	7.7	19.1	23.6
Entertainment and Communications [Member] | Transferred over Time [Member] | Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenues	229.5	235.5	690.6	709.2
IT Services and Hardware [Member] | Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenues	155.2	140.5	444.5	417.0
IT Services and Hardware [Member] | Intersegment Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Revenues	1.8	1.2	4.7	3.5
IT Services and Hardware [Member] | Transferred at Point in Time [Member] | Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenues	34.1	33.5	93.2	95.2
IT Services and Hardware [Member] | Transferred over Time [Member] | Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenues	$ 119.3	$ 105.8	$ 346.6	$ 318.3