Revenue from Contracts with Customers - Revenue by Service Offering (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenue from Contracts with Customers
Other revenue	$ 35.0	$ 31.4	$ 34.7
Total revenue	704.9	725.7	730.2
Government assistance, revenue	3.4	3.3	0.0
Subscription services
Revenue from Contracts with Customers
Revenue	648.7	672.0	672.1
Other business services
Revenue from Contracts with Customers
Revenue	21.2	22.3	23.4
Other business services - Wholesale and colocation lease revenue
Revenue from Contracts with Customers
Revenue	19.1	19.4	19.4
Residential Subscription | Subscription services
Revenue from Contracts with Customers
Revenue	537.7	561.6	566.5
Residential Subscription | HSD
Revenue from Contracts with Customers
Revenue	339.9	329.0	294.5
Government assistance, revenue	$ 3.4	$ 3.3	$ 0.0
Government Assistance, Statement of Income or Comprehensive Income	Total revenue	Total revenue	Total revenue
Residential Subscription | Video
Revenue from Contracts with Customers
Revenue	$ 173.5	$ 204.1	$ 236.4
Residential Subscription | Telephony
Revenue from Contracts with Customers
Revenue	24.3	28.5	35.6
Business Subscription | Subscription services
Revenue from Contracts with Customers
Revenue	111.0	110.4	105.6
Business Subscription | HSD
Revenue from Contracts with Customers
Revenue	72.2	70.1	64.5
Business Subscription | Video
Revenue from Contracts with Customers
Revenue	11.7	11.4	11.4
Business Subscription | Telephony
Revenue from Contracts with Customers
Revenue	$ 27.1	$ 28.9	$ 29.7