Convertible Notes (Details Textual) (USD $)	1 Months Ended	12 Months Ended		12 Months Ended			12 Months Ended			12 Months Ended
	Jun. 30, 2010	Jan. 01, 2011	Dec. 31, 2011	Dec. 31, 2011 Notes Due 2013 [Member]	Jan. 01, 2011 Notes Due 2013 [Member]	Dec. 31, 2006 Notes Due 2013 [Member]	Dec. 31, 2011 Notes Due 2011 [Member]	Jan. 01, 2011 Notes Due 2011 [Member]	Dec. 31, 2006 Notes Due 2011 [Member]	Dec. 31, 2011 Notes Due 2011 [Member] Notes Due 2013 [Member]	Jan. 01, 2011 Notes Due 2011 [Member] Notes Due 2013 [Member]	Dec. 31, 2006 Notes Due 2011 [Member] Notes Due 2013 [Member]	Dec. 31, 2011 Convertible Senior Notes Due 2015 [Member]	Jan. 01, 2011 Convertible Senior Notes Due 2015 [Member]	Jun. 30, 2010 Convertible Senior Notes Due 2015 [Member]	Dec. 31, 2011 Zero Coupon Zero Yield Senior Convertible Notes Due 2023 [Member]	Jan. 01, 2011 Zero Coupon Zero Yield Senior Convertible Notes Due 2023 [Member]	Aug. 31, 2003 Zero Coupon Zero Yield Senior Convertible Notes Due 2023 [Member]
Convertible Notes (Textual) [Abstract]
Principal amount				$ 144,461,000									$ 350,000,000	$ 350,000,000	$ 350,000,000
Stated interest rate of Convertible Senior Notes				1.50%			1.375%						2.625%
Maturity date of Convertible Senior Notes				Dec. 15, 2013			Dec. 15, 2011						Jun. 01, 2015
Event 1				Average stock closing price greater than $27.50 for at least 20 of the 30 last trading days in a calender quarter (convertible only for subsequent quarter).									Average stock closing price greater than $9.81 for at least 20 of the 30 last trading days in a fiscal quarter (convertible only for subsequent quarter).
Minimum closing price of common stock for specified days for conversion of notes				$ 27.50									$ 9.81
NET CURRENT LIABILITY OF CONVERTIBLE SENIOR NOTES													294,100,000
Minimum number of trading days limit for which closing price exceeds fixed price for conversion of notes				20 days									20 days
Number of final trading days range with in which closing price exceeds the fixed price for conversion of notes				30 days									30 days
Event 2				Specified corporate transactions occur									Specified corporate transactions
Event 3				Note trading price falls below calculated minimum									Note trading price falls below a calculated minimum.
NET LONG-TERM LIABILITY OF CONVERTIBLE SENIOR NOTES		406,404,000	131,920,000
Conversion rate of Convertible Senior Notes subject to certain conversion rate adjustments				$ 21.15									$ 7.55
Condition 1				Upon a fundamental change prior to maturity, the 2013 Note holders could require us to repurchase their notes for cash equal to the principal amount of the notes plus accrued interest. Upon certain fundamental changes, prior to maturity, if Cadence’s stock price were between $18.00 and $60.00 per share at that time, the holders of the notes would be entitled to an increase to the conversion rate. This is referred to as a “make-whole premium.”									Upon certain fundamental corporate changes prior to maturity, the 2015 Note holders could require Cadence to repurchase their notes for cash equal to the principal amount of the notes plus accrued interest. Upon certain fundamental changes prior to maturity, if Cadence’s stock price were between $6.16 and $40.00 per share at that time, the holders of the notes would be entitled to an increase to the conversion rate. This is referred to as a “make-whole premium.”
Minimum closing price of common stock to make whole premium in the form of increase to conversion rate				$ 18.00									$ 6.16
Maximum closing price of common stock to make whole premium in form of increase to conversion rate				$ 60.00									$ 40.00
Fair Value of 2015 Notes Embedded Conversion Derivative at the time of issuance															76,600,000
Proceeds From Convertible Debt	350,000,000	350,000,000
Estimated Fair Value of 2015 Notes Embedded Conversion Derivative at the balance sheet date													215,100,000	130,200,000
Cost of 2015 Notes Hedges															76,600,000
Estimated Fair Value of 2015 Notes hedges at the balance sheet date													215,100,000	130,200,000
Shares of Common Stock that can be purchased under warrants										23,600,000			46,400,000
Amount received in cash proceeds from the sale of the 2015 Warrants		37,450,000											37,500,000
Warrants to purchase shares of common stock price per share										$ 31.50			$ 10.78
Principal amount, issued						250,000,000			250,000,000						350,000,000			420,000,000
Remaining principal amount outstanding				144,500,000	144,500,000											200,000	200,000
Principal amount repurchased		205,539,000			100,000,000			100,000,000
Debt instrument decrease repayments separate transaction					5,500,000
Total expense if convertible notes are converted													63,600,000
Unamortized Debt Discount expensed if convertible notes are converted													55,900,000
Unamortized Transaction Fees expensed if convertible notes are converted													7,700,000
Total estimated fair value													527,800,000	443,000,000		200,000	200,000
Maximum purchase of Cadence's common stock shares, price per share										$ 31.50
Aggregate cost of 2011 Notes and 2013 Notes Hedges												119,800,000
Portion of sold of 2011 Notes and 2013 Notes hedges representing options to purchase Cadence's common stock											9,700,000
Proceeds received from sale of 2011 Notes and 2013 Notes Hedges											400,000
Estimated fair value of the remaining 2013 Notes Hedges				1,400,000
Amount received in cash proceeds from the sale of the 2011 Notes and 2013 Notes Warrants												39,400,000
Number of shares underlying warrants purchased with purchase of 2011 Notes and 2013 Notes											9,700,000
Cost for repurchase of portion of 2011 Notes and 2013 Notes Warrants											100,000
Notes Warrants expiration date description				various dates from February 2014 through April 2014			various dates from February 2012 through April 2012						vaious dates from September 2015 through December 2015
Total estimated fair value (including equity component)				142,300,000	133,300,000
Impact on Income statement related to fair value adjustments of 2015 Notes Embedded Conversion Derivative and 2015 Notes Hedges													0
Conversion rate of Notes				47.2813 shares of common stock per $1,000 principal amount of notes, which is equivalent to a conversion price of approximately $21.15 per share of Cadence common stock.									132.5205 shares of common stock per $1,000 principal amount of notes, which is equivalent to a conversion price of approximately $7.55 per share of Cadence common stock.
Debt instrument principal amount conversion rate for specified shares of common stock				1,000									1,000
Conversion rate for convertible senior notes per thousand principal amount of notes				47.2813									132.5205
If-converted value of Convertible Senior Notes													$ 482,400,000