Revenue Recognition - Disaggregated Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenue	$ 651.1	$ 548.1	$ 1,846.4	$ 1,544.9
Product [Member]
Disaggregation of Revenue [Line Items]
Total revenue	223.8	197.1	628.0	549.7
Service [Member]
Disaggregation of Revenue [Line Items]
Total revenue	427.3	351.0	1,218.4	995.2
Security Subscription [Member]
Disaggregation of Revenue [Line Items]
Total revenue	235.4	192.8	669.4	545.5
Technical Support and Other [Member]
Disaggregation of Revenue [Line Items]
Total revenue	$ 191.9	$ 158.2	$ 549.0	$ 449.7