Summary of Fair Value of Assets Acquired and Liabilities Assumed by Major Class (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jan. 31, 2012	Aug. 24, 2011	Aug. 24, 2011 Customer relationships	Aug. 24, 2011 Trade name	Aug. 24, 2011 User List	Aug. 24, 2011 Patent	Mar. 01, 2011 Scaleform Corporation	Mar. 01, 2011 Scaleform Corporation Developed technologies	Mar. 01, 2011 Scaleform Corporation Customer relationships	Mar. 01, 2011 Scaleform Corporation Trade name	Mar. 01, 2011 Scaleform Corporation User List	Mar. 01, 2011 Scaleform Corporation Patent	Mar. 10, 2011 Blue Ridge Numerics, Inc	Mar. 10, 2011 Blue Ridge Numerics, Inc Developed technologies	Mar. 10, 2011 Blue Ridge Numerics, Inc Customer relationships	Mar. 10, 2011 Blue Ridge Numerics, Inc Trade name	Mar. 10, 2011 Blue Ridge Numerics, Inc User List	Mar. 10, 2011 Blue Ridge Numerics, Inc Patent	Aug. 02, 2011 Instructables Corporation	Aug. 02, 2011 Instructables Corporation Developed technologies	Aug. 02, 2011 Instructables Corporation Customer relationships	Aug. 02, 2011 Instructables Corporation Trade name	Aug. 02, 2011 Instructables Corporation User List	Aug. 02, 2011 Instructables Corporation Patent	Oct. 14, 2011 Micro Application Packages Limited	Oct. 14, 2011 Micro Application Packages Limited Developed technologies	Oct. 14, 2011 Micro Application Packages Limited Customer relationships	Oct. 14, 2011 Micro Application Packages Limited Trade name	Oct. 14, 2011 Micro Application Packages Limited User List	Oct. 14, 2011 Micro Application Packages Limited Patent	Dec. 21, 2011 T-splines	Dec. 21, 2011 T-splines Developed technologies	Dec. 21, 2011 T-splines Customer relationships	Dec. 21, 2011 T-splines Trade name	Dec. 21, 2011 T-splines User List	Dec. 21, 2011 T-splines Patent	Jan. 31, 2012 Series of Individually Immaterial Business Acquisitions	Jan. 31, 2012 Series of Individually Immaterial Business Acquisitions Developed technologies	Jan. 31, 2012 Series of Individually Immaterial Business Acquisitions Customer relationships	Jan. 31, 2012 Series of Individually Immaterial Business Acquisitions Trade name	Jan. 31, 2012 Series of Individually Immaterial Business Acquisitions User List	Jan. 31, 2012 Series of Individually Immaterial Business Acquisitions Patent	Aug. 24, 2011 TurboSquid Corporation	Aug. 24, 2011 TurboSquid Corporation Developed technologies	Jan. 31, 2012 Other Entities Acquired
Business Acquisition [Line Items]
Intangible assets			$ 0	$ 0	$ 0	$ 0		$ 5.9	$ 4.4	$ 1.4	$ 0	$ 3.6		$ 6.0	$ 9.2	$ 1.1	$ 0	$ 0		$ 0.4	$ 0.2	$ 1.6	$ 5.1	$ 0		$ 2.5	$ 2.0	$ 0.9	$ 0	$ 0		$ 2.1	$ 0.7	$ 0.4	$ 0	$ 0		$ 21.7	$ 3.9	$ 1.2	$ 0	$ 0		$ 26.0
In-process research and development		0					0.6						0.6						0						0						0						0
Goodwill		0					22.6						22.3						24.4						12.7						19.8						28.3
Deferred Revenue		0					0						(1.2)						0						0						0						0
Deferred tax liability		0					(2.5)						(3.6)						(1.6)						(1.6)						0						0.2
Net tangible assets (liabilities)		0					0.2						6.8						0.1						6.5						0						(0.5)
Business Acquisition, Cost of Acquired Entity, Purchase Price							$ 36.2						$ 41.2						$ 30.2						$ 23.0						$ 23.0						$ 54.8						$ 26.0		$ 13.5
Number of Businesses Acquired	2