Revenue from Contracts with Customers - Revenue by Service Offering (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenue from Contracts with Customers
Total revenue	$ 176.1	$ 181.9	$ 350.7	$ 363.4
Subscription services
Revenue from Contracts with Customers
Revenue	163.2	168.6	325.2	336.6
Other revenue
Revenue from Contracts with Customers
Other revenue	7.5	7.6	14.8	15.5
Other business services
Revenue from Contracts with Customers
Revenue	5.4	5.7	10.7	11.3
Other business services - Wholesale and colocation lease revenue
Revenue from Contracts with Customers
Revenue	4.9	5.0	9.6	9.8
Residential Subscription | Subscription services
Revenue from Contracts with Customers
Revenue	135.4	141.3	269.7	282.0
Residential Subscription | HSD
Revenue from Contracts with Customers
Revenue	84.6	81.5	166.9	161.0
Residential Subscription | Video
Revenue from Contracts with Customers
Revenue	44.7	52.5	90.4	106.1
Residential Subscription | Telephony
Revenue from Contracts with Customers
Revenue	6.1	7.3	12.4	14.9
Business Subscription | Subscription services
Revenue from Contracts with Customers
Revenue	27.8	27.3	55.5	54.6
Business Subscription | HSD
Revenue from Contracts with Customers
Revenue	18.0	17.2	35.8	34.3
Business Subscription | Video
Revenue from Contracts with Customers
Revenue	3.0	2.8	5.9	5.6
Business Subscription | Telephony
Revenue from Contracts with Customers
Revenue	$ 6.8	$ 7.3	$ 13.8	$ 14.7