Employee Benefit Plans - Share Based Compensation by Cost and Expense Categories (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	$ 33.9	$ 70.4
Stock options
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	0.1	0.1
RSUs, RSAs, and PSAs
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	29.1	65.6
ESPP
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	4.7	4.7
Cost of revenues - Product
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	1.9	1.9
Cost of revenues - Service
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	4.5	4.8
Research and development
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	12.2	44.1
Sales and marketing
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	9.4	13.5
General and administrative
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	$ 5.9	$ 6.1