Acquisitions (Summary of Fair Value of Assets Acquired and Liabilities Assumed by Major Class) (Details) - USD ($) $ in Millions	Jul. 31, 2018	Jan. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 1,658.7	$ 1,620.2
Assemble Systems Inc
Business Acquisition [Line Items]
Goodwill	71.9
Deferred revenue (current and non-current)	(1.7)
Net tangible assets	4.2
Total	93.6
Assemble Systems Inc \| Developed technologies
Business Acquisition [Line Items]
Finite-lived intangibles	4.4
Assemble Systems Inc \| Customer relationships and other non-current intangible assets
Business Acquisition [Line Items]
Finite-lived intangibles	12.0
Assemble Systems Inc \| Trade name
Business Acquisition [Line Items]
Finite-lived intangibles	$ 2.8

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Revenue

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- Definition

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Excluding Intangible Assets And Deferrals

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The amount of identifiable intangible assets recognized as of the acquisition date.

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- Definition

Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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