Significant Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) Customer	Dec. 31, 2015 USD ($) Customer	Dec. 31, 2014 USD ($) Customer	Jan. 01, 2017 USD ($)
Significant Accounting Policies [Line Items]
Maturity of highly liquid investments	3 months
Maturity period of cash flow hedge derivatives	18 months
Period to reclassify foreign currency forward contract gain (losses) to earnings	18 months
Maturity period of foreign current derivatives	18 months
Contractual period	1 year
Warranty period for hardware products (in years)	1 year
Warranty period for software (in days)	90 days
Advertising expense	$ 15.8	$ 20.2	$ 19.2
More than likely percentage of being realized upon settlement, tax benefit	50.00%
Liability for unrecognized tax benefits as current, period	1 year
Number of customers accounting for more than 10% of revenues | Customer	0	0	0
Deferred tax assets, gross	$ 563.2	$ 551.3
Deferred revenue	$ 1,481.1	1,168.1
Shipments to Distributors [Member]
Significant Accounting Policies [Line Items]
Deferred revenue		81.8
Lack of Vendor Specific Objective Evidence [Member]
Significant Accounting Policies [Line Items]
Deferred revenue		79.5
Penalties and Acceptance Provisions [Member]
Significant Accounting Policies [Line Items]
Deferred revenue		$ 40.3
Accounting Standards Update 2016-09 [Member]
Significant Accounting Policies [Line Items]
Deferred tax assets, gross				$ 20.8
Accounting Standards Update 2016-09 [Member] | Additional Paid-in Capital [Member]
Significant Accounting Policies [Line Items]
Cumulative-effect on accumulated deficit				$ 9.0
Sales Revenue, Segment [Member] | Customer Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Number of customers accounting for more than 10% of revenues | Customer	0	0	0
Minimum [Member]
Significant Accounting Policies [Line Items]
Contractual support period	1 year
Maximum [Member]
Significant Accounting Policies [Line Items]
Contractual support period	3 years
Computer, Equipment and Software [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Useful life	1 year 6 months
Computer, Equipment and Software [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Useful life	7 years
Furniture and fixtures [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Useful life	5 years
Furniture and fixtures [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Useful life	7 years
Building and Building Improvements [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Useful life	7 years
Building and Building Improvements [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Useful life	40 years
Land Improvements [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Useful life	5 years
Land Improvements [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Useful life	40 years
Leasehold Improvements [Member]
Significant Accounting Policies [Line Items]
Useful life	10 years