Revenue from Contracts with Customers - Contract Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Costs of Obtaining Contracts with Customers
Contract liability, Beginning of period	$ 2.9	$ 2.8	$ 2.6
Deferral	12.4	8.8	9.7
Revenue recognized	(12.0)	(8.7)	(9.5)
Contract liability, End of period	3.3	2.9	2.8
Current contract liabilities	2.9	2.4
Non-current contract liabilities	0.4	0.5
Total contract liabilities	$ 3.3	$ 2.9	$ 2.8
Residential Subscription
Costs of Obtaining Contracts with Customers
Contract liability, term of contract	5 months
Business Subscription
Costs of Obtaining Contracts with Customers
Contract liability, term of contract	30 months