Revenue - Schedule of Revenues Disaggregation by Contract Type (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation Of Revenue [Line Items]
Revenues	$ 380.0	$ 384.2	$ 760.0	$ 763.8
Intersegment Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Revenues	(6.7)	(6.5)	(12.8)	(13.5)
Transferred at Point in Time [Member]
Disaggregation Of Revenue [Line Items]
Revenues	33.7	42.0	71.6	77.6
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	346.3	342.2	688.4	686.2
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	239.7	250.5	483.5	500.8
Entertainment and Communications [Member] | Intersegment Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Revenues	5.0	5.2	9.9	11.2
Entertainment and Communications [Member] | Transferred at Point in Time [Member] | Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenues	5.0	7.8	12.5	15.9
Entertainment and Communications [Member] | Transferred over Time [Member] | Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenues	229.7	237.5	461.1	473.7
IT Services and Hardware [Member] | Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenues	147.0	140.2	289.3	276.5
IT Services and Hardware [Member] | Intersegment Eliminations [Member]
Disaggregation Of Revenue [Line Items]
Revenues	1.7	1.3	2.9	2.3
IT Services and Hardware [Member] | Transferred at Point in Time [Member] | Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenues	28.7	34.2	59.1	61.7
IT Services and Hardware [Member] | Transferred over Time [Member] | Operating Segments [Member]
Disaggregation Of Revenue [Line Items]
Revenues	$ 116.6	$ 104.7	$ 227.3	$ 212.5