Significant Accounting Policies (Narrative) (Details) (USD $) In Millions, unless otherwise specified			12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2011 Online Service Agreements [Member] months	Dec. 31, 2011 Licence Update [Member] months
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenue recognition, period for recognition, average (in months)			12
Revenue recognition, period for recognition, lower end of range (in months)				12
Revenue recognition, period for recognition, higher end of range (in months)				24
Allowance for estimated product returns	$ 1.6	$ 1.4