Convertible Notes (Details Textual) (USD $)			3 Months Ended			3 Months Ended		3 Months Ended	12 Months Ended		1 Months Ended	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Notes Due 2013 [Member]	Dec. 31, 2011 Notes Due 2013 [Member]	Dec. 31, 2006 Notes Due 2013 [Member]	Mar. 31, 2012 Notes Due 2011 [Member]	Dec. 31, 2006 Notes Due 2011 [Member]	Mar. 31, 2012 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]	Jun. 30, 2010 Convertible Senior Notes Due 2015 [Member]	Mar. 31, 2012 Convertible Senior Notes Due 2015 [Member]	Apr. 02, 2011 Convertible Senior Notes Due 2015 [Member]	Dec. 31, 2011 Convertible Senior Notes Due 2015 [Member]	Mar. 31, 2012 Zero Coupon Zero Yield Senior Convertible Notes Due 2023 [Member]	Dec. 31, 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	$ 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 last 30 trading days in a calendar quarter (convertible only for subsequent quarter).									Average stock closing price greater than $9.81 for at least 20 of the last 30 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	297,653,000	294,061,000										297,700,000
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 within which closing price exceeds the fixed price for conversion of notes			30 days									30 days
Event 2			Specified corporate transactions									Specified corporate transactions
Event 3			Note trading price falls below calculated minimum									Note trading price falls below a calculated minimum.
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 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 $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
Estimated Fair Value of 2015 Notes Embedded Conversion Derivative at the balance sheet date												257,800,000		215,100,000
Cost of 2015 Notes Hedges											76,600,000
Estimated Fair Value of 2015 Notes hedges at the balance sheet date												257,800,000		215,100,000
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											37,500,000
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			144,461,000	144,461,000											200,000	200,000
Total expense if convertible notes are converted												59,500,000
Unamortized Debt Discount expensed if convertible notes are converted												52,300,000
Unamortized Transaction Fees expensed if convertible notes are converted												7,200,000
Total estimated fair value												580,800,000		527,800,000	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	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						Various dates from September 2015 through December 2015
Total estimated fair value (including equity component)			143,700,000	142,300,000
Impact on Income statement related to fair value adjustments of 2015 Notes Embedded Conversion Derivative and 2015 Notes Hedges												0	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												$ 549,200,000
Reduction in number of shares available for purchase under warrants						6,100,000