Acquisitions Summary of Fair Value of Assets Acquired and Liabilities Assumed by Major Class (Details) (USD $) In Millions, unless otherwise specified	Oct. 31, 2014	Jan. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 1,474.1	$ 1,009.9
Shotgun
Business Acquisition [Line Items]
Goodwill	43.2
Deferred revenue (current and non-current)	(0.7)
Deferred tax liability	(2.6)
Net tangible assets (liabilities)	0.1
Total	54.5
Shotgun | Developed technologies
Business Acquisition [Line Items]
Finite-lived intangibles	5.4
Shotgun | Customer relationships and other non-current intangible assets
Business Acquisition [Line Items]
Finite-lived intangibles	7.5
Shotgun | Trade name
Business Acquisition [Line Items]
Finite-lived intangibles	1.6
Within Technologies
Business Acquisition [Line Items]
Goodwill	80.6
Deferred revenue (current and non-current)	0
Deferred tax liability	(1.7)
Net tangible assets (liabilities)	(0.3)
Total	88.0
Within Technologies | Developed technologies
Business Acquisition [Line Items]
Finite-lived intangibles	4.6
Within Technologies | Customer relationships and other non-current intangible assets
Business Acquisition [Line Items]
Finite-lived intangibles	3.6
Within Technologies | Trade name
Business Acquisition [Line Items]
Finite-lived intangibles	1.2
Delcam
Business Acquisition [Line Items]
Goodwill	192.8
Deferred revenue (current and non-current)	(10.4)
Deferred tax liability	(15.3)
Net tangible assets (liabilities)	32.4
Total	284.6
Delcam | Developed technologies
Business Acquisition [Line Items]
Finite-lived intangibles	28.9
Delcam | Customer relationships and other non-current intangible assets
Business Acquisition [Line Items]
Finite-lived intangibles	39.7
Delcam | Trade name
Business Acquisition [Line Items]
Finite-lived intangibles	16.5
Other
Business Acquisition [Line Items]
Goodwill	159.6
Deferred revenue (current and non-current)	(0.2)
Deferred tax liability	(1.9)
Net tangible assets (liabilities)	(0.6)
Total	207.2
Other | Developed technologies
Business Acquisition [Line Items]
Finite-lived intangibles	35.4
Other | Customer relationships and other non-current intangible assets
Business Acquisition [Line Items]
Finite-lived intangibles	9.1
Other | Trade name
Business Acquisition [Line Items]
Finite-lived intangibles	$ 5.8