Business Segment Information (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues		$ 296.8	$ 259.4	$ 592.5	$ 509.0
Operating income (loss)		20.2	24.4	44.4	22.6
Expenditures for long-lived assets				71.0	105.2
Depreciation and amortization		50.9	47.0	102.1	92.8
Assets		2,166.1		2,166.1		$ 2,187.6
Entertainment and Communications [Member]
Segment Reporting Information [Line Items]
Revenues		173.9	181.0	348.1	356.1
Operating income (loss)		25.5	31.4	54.1	34.5
Expenditures for long-lived assets		31.8	45.5	59.4	92.3
Depreciation and amortization		41.0	40.4	81.9	79.8
Assets		1,103.8		1,103.8		1,111.4
IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Revenues		128.3	84.8	255.9	165.8
Operating income (loss)		(0.2)	(1.5)	1.2	(0.6)
Depreciation and amortization		9.9	6.5	20.1	12.9
Assets		395.9		395.9		482.7
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating income (loss)		(5.1)	(5.5)	(10.9)	(11.3)
Depreciation and amortization		0.0	0.1	0.1	0.1
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues		(5.4)	(6.4)	(11.5)	(12.9)
Intersegment Elimination [Member] | Entertainment and Communications [Member]
Segment Reporting Information [Line Items]
Revenues		4.7	5.3	9.9	10.7
Intersegment Elimination [Member] | IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Revenues		0.7	1.1	1.6	2.2
Intersegment Elimination [Member] | Corporate Segment [Member]
Segment Reporting Information [Line Items]
Assets		666.4		666.4		$ 593.5
Sales [Member] | Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues		5.4	6.4	11.5	12.9
Expenditures for Long-Lived Assets, Including Acquisitions of Businesses [Member]
Segment Reporting Information [Line Items]
Expenditures for long-lived assets	[1]	38.3	50.5	73.8	114.8
Expenditures for Long-Lived Assets, Including Acquisitions of Businesses [Member] | IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Expenditures for long-lived assets	[1]	$ 6.5	$ 5.0	$ 14.4	$ 22.5

[1] Includes cost of acquisitions