Revenue from Contracts with Customers - Costs of Obtaining Contracts (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Dec. 31, 2019
Revenue from Contracts with Customers
Capitalized contract cost, Beginning of period	$ 40.7	$ 26.3
Deferral	5.7	4.8
Amortization	(2.7)	(1.5)
Capitalized contract cost, End of period	43.7	29.6
Current costs of obtaining contracts with customers			$ 11.2	$ 10.0
Non-current costs of obtaining contracts with customers			32.5	30.7
Total costs of obtaining contracts with customers	$ 43.7	$ 29.6	$ 43.7	$ 40.7