Long-Term Debt (Details) (USD $)	9 Months Ended		12 Months Ended		3 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended
	Oct. 01, 2011	Oct. 02, 2010	Oct. 01, 2011	Dec. 31, 2010	Oct. 01, 2011 Convertible Senior Debentures 2041 [Member]	Oct. 01, 2011 Convertible Senior Debentures 2041 [Member]	Dec. 31, 2010 Convertible Senior Debentures 2041 [Member]	Oct. 01, 2011 Convertible Senior Debentures 2040 [Member]	Oct. 01, 2011 Convertible Senior Debentures 2040 [Member]	Dec. 31, 2010 Convertible Senior Debentures 2040 [Member]
Long-Term Debt [Abstract]
Credit facility	$ 180,000,000		$ 180,000,000	$ 240,000,000
Exchangeable unsecured notes, due 2102	95,042,000		95,042,000	95,042,000
Convertible senior debentures					50,330,000	50,330,000	0	98,068,000	98,068,000	96,640,000
Long-term debt, gross, excluding derivative liabilities	422,500,000		422,500,000	431,400,000
Less current portion	0		0	0
Long-term debt, less current portion	423,440,000		423,440,000	431,682,000
Debt Instrument [Line Items]
Convertible senior debentures issuance date						May 13, 2011			November 9, 2010
Principal amount of convertible senior debentures					150,000,000	150,000,000		275,000,000	275,000,000	275,000,000
Common stock, shares repurchased (in shares)	8,620,689
Treasury stock, value, acquired, cost method						150,000,000
Principal amount of the debentures					150,000,000	150,000,000		275,000,000	275,000,000	275,000,000
Unamortized discount					(100,044,000)	(100,044,000)		(177,529,000)	(177,529,000)	(178,679,000)
Embedded derivative	971,000		971,000		374,000	374,000		597,000	597,000	319,000
Carrying value of liability component					50,330,000	50,330,000	0	98,068,000	98,068,000	96,640,000
Equity component - net carrying value					61,758,000	61,758,000		110,094,000	110,094,000	110,094,000
Stated rate of interest on convertible senior debentures (in hundredths)					2.25%	2.25%		2.25%	2.25%
Effective rate of interest on convertible senior debentures (in hundredths)						8.375%			8.00%
Contractual coupon interest					844,000	1,285,000		1,547,000	4,641,000
Non-cash amortization of debt discount	1,448,000	0			196,000	298,000		391,000	1,150,000
Non-cash amortization of deferred financing costs					12,000	18,000		22,000	66,000
Non-cash change in value of derivative liability					161,000	163,000		270,000	278,000
Total interest expense related to the debentures					1,213,000	1,764,000		2,230,000	6,135,000
Debt instrument percentage of conversion price (in hundredths)					130.00%	130.00%
Debt instrument, conversion price amount					24.73
Debt instrument, Percentage of sale price of common stock (in hundredths)					98.00%	98.00%
Debt instrument, initial conversion shares of common stock					52.5659	52.5659
Debt instrument, principal amount of debentures					1,000	1,000
Debt instrument, initial conversion price (in dollars per share)					$ 19.02	$ 19.02
Debt instrument, percentage of initial conversion price premium (in hundredths)					12.50%	12.50%
Debt instrument, conversion price (in dollars per share)					$ 16.91	$ 16.91
Maximum Share Repurchase Authority Under Credit Facility	300,000,000		300,000,000
Debt instrument decrease repyaments		10,000,000
Debt Instrument Balance Israeli Bank Loan		13,500,000
Leverage ratio requirement for credit facility			2.75 to 1.00
Interest expense ratio for credit facility			2.00 to 1.00
Available liquidity requirement for credit facility	$ 400,000,000		$ 400,000,000