Long-Term Debt (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Apr. 02, 2016 USD ($) shares $ / shares	Apr. 04, 2015 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Credit facility	$ 178,000		$ 190,000
Exchangeable unsecured notes, due 2102	12,436		38,642
Deferred Financing Costs	(12,214)		(12,659)
Long-term debt	400,124		436,738
Less current portion	0		0
Long-term debt, less current portion	400,124		436,738
Debt Instruments [Abstract]
Principal amount of debt	$ 575,000		575,000
Debt instrument percentage of conversion price (in hundredths)	130.00%
Debt instrument, Percentage of sale price of common stock (in hundredths)	98.00%
Principal payments on long-term debt and capital leases	$ (22,595)	$ 0
Liability and equity components of convertible debentures [Abstract]
Principal amount of the debentures	575,000		575,000
Unamortized discount	(354,441)		(355,561)
Embedded derivative	1,343		1,316
Carrying value of liability component	221,902		220,755
Equity component - net carrying value	230,214		230,214
Interest expense related to debentures [Abstract]
Contractual coupon interest	3,235	3,235
Non-cash amortization of debt discount	1,120	1,036
Non-cash amortization of deferred financing costs	46	47
Non-cash change in value of derivative liability	27	(53)
Total interest expense related to the debentures	4,428	4,265
Convertible Senior Debentures, Due 2040 [Member]
Debt Instrument [Line Items]
Convertible Debt, Noncurrent	$ 106,573		106,011
Debt Instruments [Abstract]
Issuance date	Nov. 09, 2010
Debt maturity date	Nov. 15, 2040
Principal amount of debt	$ 275,000		275,000
Stated rate of interest on debt (in hundredths)	2.25%
Effective rate of interest on convertible senior debentures (in hundredths)	8.00%
Debt conversion rate	75.1038
Debt effective conversion price | $ / shares	$ 13.31
Debt Instrument, Convertible, Stock Price Trigger | $ / shares	$ 17.30
Convertible senior debentures call date	Nov. 20, 2020
Liability and equity components of convertible debentures [Abstract]
Principal amount of the debentures	$ 275,000		275,000
Unamortized discount	(169,009)		(169,565)
Embedded derivative	582		576
Carrying value of liability component	106,573		106,011
Equity component - net carrying value	110,094		110,094
Interest expense related to debentures [Abstract]
Contractual coupon interest	1,547	1,547
Non-cash amortization of debt discount	556	515
Non-cash amortization of deferred financing costs	22	22
Non-cash change in value of derivative liability	6	(59)
Total interest expense related to the debentures	2,131	2,025
Convertible Senior Debentures, Due 2041 [Member]
Debt Instrument [Line Items]
Convertible Debt, Noncurrent	$ 54,746		54,424
Debt Instruments [Abstract]
Issuance date	May 13, 2011
Debt maturity date	May 15, 2041
Principal amount of debt	$ 150,000		150,000
Stated rate of interest on debt (in hundredths)	2.25%
Effective rate of interest on convertible senior debentures (in hundredths)	8.375%
Debt conversion rate	54.8068
Debt effective conversion price | $ / shares	$ 18.25
Debt Instrument, Convertible, Stock Price Trigger | $ / shares	$ 23.73
Convertible senior debentures call date	May 20, 2021
Liability and equity components of convertible debentures [Abstract]
Principal amount of the debentures	$ 150,000		150,000
Unamortized discount	(95,730)		(96,014)
Embedded derivative	476		438
Carrying value of liability component	54,746		54,424
Equity component - net carrying value	62,246		62,246
Interest expense related to debentures [Abstract]
Contractual coupon interest	844	844
Non-cash amortization of debt discount	284	261
Non-cash amortization of deferred financing costs	11	12
Non-cash change in value of derivative liability	38	13
Total interest expense related to the debentures	1,177	1,130
Convertible Senior Debentures, Due 2042 [Member]
Debt Instrument [Line Items]
Convertible Debt, Noncurrent	$ 60,583		60,320
Debt Instruments [Abstract]
Issuance date	May 31, 2012
Debt maturity date	Jun. 01, 2042
Principal amount of debt	$ 150,000		150,000
Stated rate of interest on debt (in hundredths)	2.25%
Effective rate of interest on convertible senior debentures (in hundredths)	7.50%
Debt conversion rate	88.3041
Debt effective conversion price | $ / shares	$ 11.32
Debt Instrument, Convertible, Stock Price Trigger | $ / shares	$ 14.72
Convertible senior debentures call date	Jun. 07, 2022
Liability and equity components of convertible debentures [Abstract]
Principal amount of the debentures	$ 150,000		150,000
Unamortized discount	(89,702)		(89,982)
Embedded derivative	285		302
Carrying value of liability component	60,583		60,320
Equity component - net carrying value	57,874		$ 57,874
Interest expense related to debentures [Abstract]
Contractual coupon interest	844	844
Non-cash amortization of debt discount	280	260
Non-cash amortization of deferred financing costs	13	13
Non-cash change in value of derivative liability	(17)	(7)
Total interest expense related to the debentures	$ 1,120	$ 1,110
Exchangeable Unsecured Notes, Due 2102 [Member]
Debt Instruments [Abstract]
Issuance date	Dec. 13, 2002
Debt Instrument, Convertible, Stock Price Trigger | $ / shares	$ 15.39
Principal amount of repurchased debt	$ 26,206
Principal payments on long-term debt and capital leases	$ 22,595
Repurchase Date	Mar. 31, 2016
Number of shares of common stock the Notes are exchangeable into (in shares) | shares	808,000
Repurchased notes shares exchangeable | shares	1,702,813