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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

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Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, resulting from a business combination.

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The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

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Business Combinations (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
Business Acquisition [Line Items]
Goodwill	599,929us-gaap_Goodwill	$ 549,044us-gaap_Goodwill	$ 535,932us-gaap_Goodwill
Berkeley Design Automation, Inc. [Member]
Business Acquisition [Line Items]
Fair Value Inputs, Discount Rate	15.00%
Developed Technology Rights [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Finite-Lived Intangibles	11,200
Finite-Lived intangible asset, useful life	5 years
Other Intangible Assets
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Finite-Lived Intangibles	13,570
Berkeley Design Automation, Inc. [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Mar. 20, 2014
Payments to Acquire Businesses, Gross	46,832
AcquisitionRelatedDeferredPayment	4,471
Business Combination, Consideration Transferred	51,303
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	2,335
Business Combination, Recognized Identifiable Finite-Lived Intangibles	24,770
Goodwill	24,198
Other Acquired Entities [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	49,315
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	876
Business Combination, Recognized Identifiable Finite-Lived Intangibles	15,160
Goodwill	33,279
Total FY15 Acquisitions [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	100,618
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	3,211
Business Combination, Recognized Identifiable Finite-Lived Intangibles	39,930
Goodwill	57,477
Minimum \| Other Intangible Assets
Business Acquisition [Line Items]
Finite-Lived intangible asset, useful life	2 years
Maximum \| Other Intangible Assets
Business Acquisition [Line Items]
Finite-Lived intangible asset, useful life	5 years