Revenue - Contract Balances (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Contract Asset [Roll Forward]
Capitalized Contract Cost, Net, Beginning Balance	$ 32.5	$ 32.4	$ 32.4
Capitalized Contract Cost, Additions	6.7	5.5	5.5
Capitalized Contract Cost, Amortization	(5.5)	(5.4)	(5.5)
Capitalized Contract Cost, Net, Ending Balance	33.7	32.5	32.4
Contract with Customer, Liability, Current	1.5
Contract with Customer, Liability, Noncurrent	28.3
Fulfillment Costs [Member]
Contract Asset [Roll Forward]
Capitalized Contract Cost, Net, Beginning Balance	19.2	19.4	19.5
Capitalized Contract Cost, Additions	3.8	3.4	3.5
Capitalized Contract Cost, Amortization	(3.6)	(3.6)	(3.6)
Capitalized Contract Cost, Net, Ending Balance	19.4	19.2	19.4
Cost of Acquisition [Member]
Contract Asset [Roll Forward]
Capitalized Contract Cost, Net, Beginning Balance	13.3	13.0	12.9
Capitalized Contract Cost, Additions	2.9	2.1	2.0
Capitalized Contract Cost, Amortization	(1.9)	(1.8)	(1.9)
Capitalized Contract Cost, Net, Ending Balance	14.3	13.3	13.0
Entertainment and Communications [Member]
Contract Asset [Roll Forward]
Capitalized Contract Cost, Net, Beginning Balance	28.7	28.8	29.1
Capitalized Contract Cost, Additions	5.5	4.8	4.7
Capitalized Contract Cost, Amortization	(4.8)	(4.9)	(5.0)
Capitalized Contract Cost, Net, Ending Balance	29.4	28.7	28.8
Entertainment and Communications [Member] | Fulfillment Costs [Member]
Contract Asset [Roll Forward]
Capitalized Contract Cost, Net, Beginning Balance	17.0	17.3	17.5
Capitalized Contract Cost, Additions	3.2	3.0	3.1
Capitalized Contract Cost, Amortization	(3.2)	(3.3)	(3.3)
Capitalized Contract Cost, Net, Ending Balance	17.0	17.0	17.3
Entertainment and Communications [Member] | Cost of Acquisition [Member]
Contract Asset [Roll Forward]
Capitalized Contract Cost, Net, Beginning Balance	11.7	11.5	11.6
Capitalized Contract Cost, Additions	2.3	1.8	1.6
Capitalized Contract Cost, Amortization	(1.6)	(1.6)	(1.7)
Capitalized Contract Cost, Net, Ending Balance	12.4	11.7	11.5
IT Services and Hardware [Member]
Contract Asset [Roll Forward]
Capitalized Contract Cost, Net, Beginning Balance	3.8	3.6	3.3
Capitalized Contract Cost, Additions	1.2	0.7	0.8
Capitalized Contract Cost, Amortization	(0.7)	(0.5)	(0.5)
Capitalized Contract Cost, Net, Ending Balance	4.3	3.8	3.6
IT Services and Hardware [Member] | Fulfillment Costs [Member]
Contract Asset [Roll Forward]
Capitalized Contract Cost, Net, Beginning Balance	2.2	2.1	2.0
Capitalized Contract Cost, Additions	0.6	0.4	0.4
Capitalized Contract Cost, Amortization	(0.4)	(0.3)	(0.3)
Capitalized Contract Cost, Net, Ending Balance	2.4	2.2	2.1
IT Services and Hardware [Member] | Cost of Acquisition [Member]
Contract Asset [Roll Forward]
Capitalized Contract Cost, Net, Beginning Balance	1.6	1.5	1.3
Capitalized Contract Cost, Additions	0.6	0.3	0.4
Capitalized Contract Cost, Amortization	(0.3)	(0.2)	(0.2)
Capitalized Contract Cost, Net, Ending Balance	$ 1.9	$ 1.6	$ 1.5