Acquisitions (Details Textual) (USD $)	12 Months Ended			12 Months Ended			12 Months Ended		12 Months Ended
	Dec. 31, 2011	Jan. 01, 2011	Jan. 02, 2010	Dec. 31, 2011 Denali Software Inc [Member]	Jan. 01, 2011 Denali Software Inc [Member]	Jun. 30, 2010 Denali Software Inc [Member]	Dec. 31, 2011 2011 Acquisitions [Member] Y	Jan. 01, 2011 2011 Acquisitions [Member]	Jan. 01, 2011 Other 2010 Acquisition [Member] Y	Dec. 31, 2011 Other 2010 Acquisition [Member]
Acquisitions (Textual) [Abstract]
Initial Purchase Price of Acquisition, cash paid						$ 296,800,000	$ 49,300,000
Goodwill						152,172,000	32,300,000		3,900,000
Intangible assets associated with 2011 acquisitions							21,600,000		2,200,000
Goodwill not expected to be deductible for income tax purpose						152,200,000	32,300,000		3,900,000
Maximum payments for contingent consideration arrangement							5,000,000		4,000,000
Time of certain financial measures subsequent to the consummation of the acquisition related to contingent consideration							3 years
Acquisition related contingent consideration at initial fair value								3,500,000	800,000
Beginning date of acquisition related contingent consideration measurement period							"Subsequent to October 1, 2011"
Acquisition-related contingent consideration at fair value	3,911,000	966,000	0				3,700,000			200,000
Accretion recorded after the date of acquisition		108,000					200,000
Additional Payments deferred on the acquisition date						12,600,000
Business combination separately recognized transactions additional disclosures acquisition costs, Unpaid				800,000
Business combination, separately recognized transactions, acquisition cost expensed				1,500,000	10,200,000
Business combination, separately recognized transactions, acquisition cost potential expense In future periods				900,000
Maximum Amount obligated to pay by Cadence	30,700,000
Period over which consideration may be paid	52 months
Portion of amount of contingent consideration potential expense in future periods	20,600,000
Business combination contingent consideration arrangements maximum potential goodwill	5,600,000
Cash and cash equivalents included in acquired current assets						46,700,000
Trade receivables included in acquired current assets						11,100,000
Deferred Revenue						11,300,000
Deferred Tax Liabilities, Goodwill and Intangible Assets, Intangible Assets	(66,878,000)	(66,901,000)
Deferred tax related to intangible assets acquired with Denali						66,700,000
Intangible assets allocated to in - process research and development									500,000
Acquired Intangibles									1,700,000
Weighted-average life of finite- lived intangible assets							7		5
Decrease in valuation allowance against deferred tax assets					$ 66,700,000