Long-Term Debt (Details) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended
	Jul. 02, 2016 USD ($) shares $ / shares	Apr. 02, 2016 USD ($)	Jul. 04, 2015 USD ($)	Jul. 02, 2016 USD ($) shares $ / shares	Jul. 04, 2015 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Credit facility	$ 124,000			$ 124,000		$ 190,000
Exchangeable unsecured notes, due 2102	0			0		38,642
Deferred Financing Costs	(11,770)			(11,770)		(12,659)
Long-term debt	335,144			335,144		436,738
Less current portion	0			0		0
Long-term debt, less current portion	335,144			335,144		436,738
Debt Instruments [Abstract]
Principal amount of debt	$ 575,000			$ 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%			98.00%
Principal payments on long-term debt and capital leases				$ (34,044)	$ 0
Liability and equity components of convertible debentures [Abstract]
Principal amount of the debentures	$ 575,000			575,000		575,000
Unamortized discount	(353,302)			(353,302)		(355,561)
Embedded derivative	1,216			1,216		1,316
Carrying value of liability component	222,914			222,914		220,755
Equity component - net carrying value	230,214			230,214		230,214
Interest expense related to debentures [Abstract]
Contractual coupon interest	3,235		$ 3,235	6,470	6,470
Non-cash amortization of debt discount	1,139		1,054	2,259	2,090
Non-cash amortization of deferred financing costs	49		48	95	95
Non-cash change in value of derivative liability	(127)		335	(100)	282
Total interest expense related to the debentures	4,296		4,672	8,724	8,937
Convertible Senior Debentures, Due 2040 [Member]
Debt Instrument [Line Items]
Convertible Debt, Noncurrent	107,099			$ 107,099		106,011
Debt Instruments [Abstract]
Issuance date				Nov. 09, 2010
Debt maturity date				Nov. 15, 2040
Principal amount of debt	$ 275,000			$ 275,000		275,000
Stated rate of interest on debt (in hundredths)	2.25%			2.25%
Effective rate of interest on convertible senior debentures (in hundredths)	8.00%			8.00%
Debt conversion rate	75.4595
Debt effective conversion price | $ / shares	$ 13.25			$ 13.25
Debt Instrument, Convertible, Stock Price Trigger | $ / shares				$ 17.23
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		275,000
Unamortized discount	(168,442)			(168,442)		(169,565)
Embedded derivative	541			541		576
Carrying value of liability component	107,099			107,099		106,011
Equity component - net carrying value	110,094			110,094		110,094
Interest expense related to debentures [Abstract]
Contractual coupon interest	1,547		1,547	3,094	3,094
Non-cash amortization of debt discount	567		524	1,123	1,039
Non-cash amortization of deferred financing costs	22		22	44	44
Non-cash change in value of derivative liability	(41)		165	(35)	106
Total interest expense related to the debentures	2,095		2,258	4,226	4,283
Convertible Senior Debentures, Due 2041 [Member]
Debt Instrument [Line Items]
Convertible Debt, Noncurrent	54,963			$ 54,963		54,424
Debt Instruments [Abstract]
Issuance date				May 13, 2011
Debt maturity date				May 15, 2041
Principal amount of debt	$ 150,000			$ 150,000		150,000
Stated rate of interest on debt (in hundredths)	2.25%			2.25%
Effective rate of interest on convertible senior debentures (in hundredths)	8.375%			8.375%
Debt conversion rate	55.0664
Debt effective conversion price | $ / shares	$ 18.16			$ 18.16
Debt Instrument, Convertible, Stock Price Trigger | $ / shares				$ 23.61
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		150,000
Unamortized discount	(95,441)			(95,441)		(96,014)
Embedded derivative	404			404		438
Carrying value of liability component	54,963			54,963		54,424
Equity component - net carrying value	62,246			62,246		62,246
Interest expense related to debentures [Abstract]
Contractual coupon interest	844		844	1,688	1,688
Non-cash amortization of debt discount	289		267	573	528
Non-cash amortization of deferred financing costs	13		12	24	24
Non-cash change in value of derivative liability	(72)		124	(34)	137
Total interest expense related to the debentures	1,074		1,247	2,251	2,377
Convertible Senior Debentures, Due 2042 [Member]
Debt Instrument [Line Items]
Convertible Debt, Noncurrent	60,852			$ 60,852		60,320
Debt Instruments [Abstract]
Issuance date				May 31, 2012
Debt maturity date				Jun. 01, 2042
Principal amount of debt	$ 150,000			$ 150,000		150,000
Stated rate of interest on debt (in hundredths)	2.25%			2.25%
Effective rate of interest on convertible senior debentures (in hundredths)	7.50%			7.50%
Debt conversion rate	88.7223
Debt effective conversion price | $ / shares	$ 11.27			$ 11.27
Debt Instrument, Convertible, Stock Price Trigger | $ / shares				$ 14.65
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		150,000
Unamortized discount	(89,419)			(89,419)		(89,982)
Embedded derivative	271			271		302
Carrying value of liability component	60,852			60,852		60,320
Equity component - net carrying value	57,874			57,874		$ 57,874
Interest expense related to debentures [Abstract]
Contractual coupon interest	844		844	1,688	1,688
Non-cash amortization of debt discount	283		263	563	523
Non-cash amortization of deferred financing costs	14		14	27	27
Non-cash change in value of derivative liability	(14)		46	(31)	39
Total interest expense related to the debentures	1,127		$ 1,167	2,247	$ 2,277
Exchangeable Unsecured Notes, Due 2102 [Member]
Debt Instruments [Abstract]
Principal amount of repurchased debt	12,436	$ 26,206		$ 12,436
Principal payments on long-term debt and capital leases	$ 11,449	$ 22,595
Repurchase Date	Jun. 28, 2016	Mar. 31, 2016
Repurchased notes shares exchangeable | shares	807,995			2,510,808