Significant Accounting Policies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) customer	Dec. 31, 2014 USD ($) customer	Dec. 31, 2013 USD ($)
Significant Accounting Policies [Line Items]
Allowance for doubtful accounts	$ 6.3	$ 3.8
Estimated useful lives of intangible assets	6 years 3 months 7 days	6 years 5 months 20 days
Amount capitalized related to internal use software	$ 93.9	$ 79.1
Amount expensed related to internal use software	81.8	66.8	$ 58.6
Allowance for estimated product returns	1.4	2.2
Advertising costs	144.1	150.1	146.5
Foreign postretirement benefit plans
Significant Accounting Policies [Line Items]
Termination indemnities	13.8	15.6
Termination indemnities, compensation expense	$ 3.8	$ 3.2	$ 3.5
Online service agreements
Significant Accounting Policies [Line Items]
Revenue recognition, period for recognition	12 months
Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets	3 years
Licensing agreement term	1 year
Minimum | License update
Significant Accounting Policies [Line Items]
Revenue recognition, period for recognition	12 months
Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets	7 years
Licensing agreement term	5 years
Maximum | License update
Significant Accounting Policies [Line Items]
Revenue recognition, period for recognition	24 months
Weighted average | Online service agreements
Significant Accounting Policies [Line Items]
Revenue recognition, period for recognition	12 months
Customer concentration risk | Accounts receivable
Significant Accounting Policies [Line Items]
Number of customers meeting concentration risk threshold | customer	0	2
Customer concentration risk | Accounts receivable | Arrow Group
Significant Accounting Policies [Line Items]
Concentration risk percentage		11.00%
Customer concentration risk | Accounts receivable | Ingram Micro
Significant Accounting Policies [Line Items]
Concentration risk percentage		10.00%