Revenue from Contracts with Customers - Costs of Obtaining Contracts (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Dec. 31, 2020
Revenue from Contracts with Customers
Capitalized contract cost, Beginning of period	$ 49.6	$ 40.7
Deferral	4.9	5.7
Amortization	(3.6)	(2.7)
Capitalized contract cost, End of period	50.9	43.7
Current costs of obtaining contracts with customers			$ 16.7	$ 15.3
Non-current costs of obtaining contracts with customers			34.2	34.3
Total costs of obtaining contracts with customers	$ 49.6	$ 43.7	$ 50.9	$ 49.6