Long-Term Debt (Details) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended
	Oct. 01, 2016 USD ($) $ / shares	Jul. 02, 2016 USD ($)	Apr. 02, 2016 USD ($)	Oct. 03, 2015 USD ($)	Jul. 02, 2016 USD ($) shares	Oct. 01, 2016 USD ($) $ / shares	Oct. 03, 2015 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Credit facility	$ 149,000					$ 149,000		$ 190,000
Exchangeable unsecured notes, due 2102	0					0		38,642
Deferred Financing Costs	(11,325)					(11,325)		(12,659)
Long-term debt	361,467					361,467		436,738
Less current portion	0					0		0
Long-term debt, less current portion	361,467					361,467		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	(352,136)					(352,136)		(355,561)
Embedded derivative	928					928		1,316
Carrying value of liability component	223,792					223,792		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		9,705	9,705
Non-cash amortization of debt discount	1,166			1,077		3,425	3,167
Non-cash amortization of deferred financing costs	46			47		141	142
Non-cash change in value of derivative liability	(288)			395		(388)	677
Total interest expense related to the debentures	4,159			4,754		12,883	13,691
Convertible Senior Debentures, Due 2040 [Member]
Debt Instrument [Line Items]
Convertible Debt, Noncurrent	107,563					$ 107,563		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	75.8043
Debt effective conversion price | $ / shares	$ 13.19					$ 13.19
Debt Instrument, Convertible, Stock Price Trigger | $ / shares						$ 17.15
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	(167,863)					(167,863)		(169,565)
Embedded derivative	426					426		576
Carrying value of liability component	107,563					107,563		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		4,641	4,641
Non-cash amortization of debt discount	579			535		1,702	1,574
Non-cash amortization of deferred financing costs	22			22		66	66
Non-cash change in value of derivative liability	(115)			198		(150)	304
Total interest expense related to the debentures	2,033			2,302		6,259	6,585
Convertible Senior Debentures, Due 2041 [Member]
Debt Instrument [Line Items]
Convertible Debt, Noncurrent	55,157					$ 55,157		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	55.3180
Debt effective conversion price | $ / shares	$ 18.08					$ 18.08
Debt Instrument, Convertible, Stock Price Trigger | $ / shares						$ 23.50
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	(95,145)					(95,145)		(96,014)
Embedded derivative	302					302		438
Carrying value of liability component	55,157					55,157		54,424
Equity component - net carrying value	62,246					62,246		62,246
Interest expense related to debentures [Abstract]
Contractual coupon interest	844			844		2,532	2,532
Non-cash amortization of debt discount	296			272		869	800
Non-cash amortization of deferred financing costs	11			12		35	36
Non-cash change in value of derivative liability	(102)			92		(136)	229
Total interest expense related to the debentures	1,049			1,220		3,300	3,597
Convertible Senior Debentures, Due 2042 [Member]
Debt Instrument [Line Items]
Convertible Debt, Noncurrent	61,072					$ 61,072		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	89.1277
Debt effective conversion price | $ / shares	$ 11.22					$ 11.22
Debt Instrument, Convertible, Stock Price Trigger | $ / shares						$ 14.59
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	(89,128)					(89,128)		(89,982)
Embedded derivative	200					200		302
Carrying value of liability component	61,072					61,072		60,320
Equity component - net carrying value	57,874					57,874		$ 57,874
Interest expense related to debentures [Abstract]
Contractual coupon interest	844			844		2,532	2,532
Non-cash amortization of debt discount	291			270		854	793
Non-cash amortization of deferred financing costs	13			13		40	40
Non-cash change in value of derivative liability	(71)			105		(102)	144
Total interest expense related to the debentures	$ 1,077			$ 1,232		$ 3,324	$ 3,509
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					2,510,808