Plant, Property and Equipment, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Plant, Property and Equipment, Net
Total plant, property and equipment	$ 3,013.7	$ 2,809.0
Less accumulated depreciation	(1,940.0)	(1,755.6)
Plant, Property and Equipment, Net	1,073.7	1,053.4
Depreciation expense	204.4	185.1	$ 196.2
Loss (gain) on write offs or sales of head-end and customer premise equipment	2.4	0.6	$ 0.6
Distribution facilities
Plant, Property and Equipment, Net
Total plant, property and equipment	1,780.7	1,543.3
Customer premise equipment
Plant, Property and Equipment, Net
Total plant, property and equipment	460.1	440.4
Head-end equipment
Plant, Property and Equipment, Net
Total plant, property and equipment	341.2	321.9
Telephony infrastructure
Plant, Property and Equipment, Net
Total plant, property and equipment	97.9	94.8
Computer equipment and software
Plant, Property and Equipment, Net
Total plant, property and equipment	146.4	129.1
Vehicles
Plant, Property and Equipment, Net
Total plant, property and equipment	37.0	36.5
Buildings and leasehold improvements
Plant, Property and Equipment, Net
Total plant, property and equipment	49.5	46.3
Office and technical equipment
Plant, Property and Equipment, Net
Total plant, property and equipment	33.5	32.7
Land
Plant, Property and Equipment, Net
Total plant, property and equipment	6.2	6.2
Construction in progress (including material inventory and other)
Plant, Property and Equipment, Net
Total plant, property and equipment	$ 61.2	$ 157.8