Acquisitions (Narrative) (Details) (USD $)	12 Months Ended			1 Months Ended				1 Months Ended			0 Months Ended				3 Months Ended
	Dec. 31, 2011 Netviewer AG [Member]	Dec. 31, 2010 Netviewer AG [Member]	Feb. 28, 2011 Netviewer AG [Member]	Jul. 31, 2011 Cloud.com [Member]	Oct. 31, 2011 ShareFile [Member]	Nov. 30, 2011 App-DNA [Member]	Mar. 31, 2011 Other Acquisition [Member]	Aug. 31, 2011 Ringcube [Member]	May 31, 2011 Kaviza, Inc. [Member]	May 31, 2011 Kaviza, Inc. [Member] Escrow Deposits [Member]	Sep. 07, 2010 VMLogix, Inc. [Member]	Sep. 07, 2010 VMLogix, Inc. [Member] Product Related Technologies [Member] years	Sep. 07, 2010 VMLogix, Inc. [Member] Other Intangible Assets [Member] years	Mar. 31, 2010 Series Of Individually Immaterial Business Acquisitions [Member]	Mar. 31, 2010 Series Of Individually Immaterial Business Acquisitions [Member] Product Related Technologies [Member] years	Mar. 31, 2010 Series Of Individually Immaterial Business Acquisitions [Member] Other Intangible Assets [Member] years
Total consideration in business acquisitions			$ 107,500,000	$ 158,800,000	$ 54,500,000	$ 91,300,000	$ 10,500,000	$ 32,200,000			$ 13,200,000			$ 9,200,000
Cash acquired in business combination			6,300,000	5,600,000	1,700,000	3,200,000		500,000
Transaction costs			3,100,000	2,900,000	700,000	1,300,000		600,000
Direct cost of business acquisition including legal, accounting and other costs	1,100,000	2,000,000
Cash consideration in business acquisitions											10,400,000
VMLogix liabilities settled in conjunction with the acquisition											2,800,000
Assets acquired			152,485,000	200,220,000	80,404,000	117,220,000					11,900,000			9,400,000
Intangible assets			28,806,000	89,000,000	28,200,000	44,760,000					7,500,000	6,200,000	1,300,000	7,100,000	6,200,000	900,000
Weighted average life (in years)												5.0	4.0		5.0	2.0
Goodwill			98,725,000	100,649,000	49,879,000	58,204,000					6,400,000			2,600,000
Liabilities assumed											5,100,000			2,800,000
Equity interest in subsidiary									100.00%
Unvested stock options assumed in business acquisition									88,687		47,784
Additional investment in the consolidated subsidiary									$ 17,200,000	$ 3,000,000
Stock units converted and assumed	99,100			288,742	180,697	114,487		58,439	33,301
Stock options converted and assumed				183,780	390,775