Plant, Property and Equipment, Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Plant, Property and Equipment, Net
Total plant, property and equipment	$ 3,065.6		$ 3,013.7
Less accumulated depreciation	(1,991.2)		(1,940.0)
Plant, Property and Equipment, Net	1,074.4		1,073.7
Depreciation expense	55.4	$ 49.2
Distribution facilities
Plant, Property and Equipment, Net
Total plant, property and equipment	1,846.3		1,780.7
Customer premise equipment
Plant, Property and Equipment, Net
Total plant, property and equipment	465.3		460.1
Head-end equipment
Plant, Property and Equipment, Net
Total plant, property and equipment	342.4		341.2
Telephony infrastructure
Plant, Property and Equipment, Net
Total plant, property and equipment	98.1		97.9
Computer equipment and software
Plant, Property and Equipment, Net
Total plant, property and equipment	150.6		146.4
Vehicles
Plant, Property and Equipment, Net
Total plant, property and equipment	36.0		37.0
Buildings and leasehold improvements
Plant, Property and Equipment, Net
Total plant, property and equipment	49.5		49.5
Office and technical equipment
Plant, Property and Equipment, Net
Total plant, property and equipment	34.2		33.5
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	$ 37.0		$ 61.2