Property and Equipment—Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	$ 521.1		$ 481.3
Less: accumulated depreciation	(146.9)		(137.0)
Property and equipment - net	374.2		344.3
Depreciation expense	13.6	$ 12.7
Land [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	93.3		93.3
Building and building improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	148.0		147.4
Computer equipment and software [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	121.7		116.7
Leasehold improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	26.8		25.5
Evaluation units [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	22.4		19.9
Furniture and fixtures [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	18.2		17.3
Construction-in-progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	$ 90.7		$ 61.2