Long-Term Debt (Details) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Oct. 03, 2020 USD ($) $ / shares	Apr. 04, 2020 USD ($)	Sep. 28, 2019 USD ($)	Oct. 03, 2020 USD ($) $ / shares	Sep. 28, 2019 USD ($)	Dec. 31, 2019 USD ($)
Debt Instruments [Abstract]
Credit facility	$ 0			$ 0		$ 0
Deferred financing costs	(12,249)			(12,249)		(16,784)
Long-term debt	392,290			392,290		499,147
Less current portion	0			0		0
Long-term debt, less current portion	392,290			392,290		499,147
Interest expense [Abstract]
Contractual coupon interest	2,855		$ 3,493	9,556	$ 10,510
Non-cash amortization of debt discount	3,107		3,573	10,232	10,558
Other non-cash interest expense (income)	382		446	1,271	1,336
Total interest expense related to the debentures	6,344		7,512	21,059	22,404
Purchase price of extinguished debt				148,177	22,695
Allocated liability component of repurchased debt		$ 8,452
Allocated equity component of repurchased debt		11,397
Loss on extinguishment of debt, including the write-off of portion of unamortized debt issuance costs	(3,454)	$ (2,920)	0	(7,520)	(1,307)
Convertible Senior Notes, Due 2025 [Member]
Debt Instruments [Abstract]
Convertible debt	$ 403,345			$ 403,345		509,128
Issuance date				Jun. 12, 2018
Debt maturity date				Jun. 15, 2025
Cash coupon rate	2.25%			2.25%
Nonconvertible debt borrowing rate at issuance	5.50%			5.50%
Effective conversion rate				31.8674
Effective conversion price (in dollars per share) | $ / shares	$ 31.38			$ 31.38
130% of the conversion price (in dollars per share) | $ / shares				$ 40.79
Debt instrument percentage of conversion price				130.00%
Debt instrument percentage of sales price of common stock	98.00%			98.00%
Maximum threshold of quarterly cash dividends per share of common stock for not adjusting conversion rate of convertible notes | $ / shares				$ 0.085
Liability and equity components of convertible debentures [Abstract]
Principal amount of debt	$ 465,344			$ 465,344
Interest expense [Abstract]
Contractual coupon interest	2,839		3,375	9,480	10,125
Non-cash amortization of debt discount	3,099		3,520	10,195	10,388
Other non-cash interest expense (income)	382		454	1,271	1,362
Total interest expense related to the debentures	6,320		7,349	20,946	21,875
Principal amount of repurchased debt	58,886			134,656
Net carrying value of repurchased debt	50,922			115,978
Purchase price of extinguished debt	57,652			128,328
Allocated liability component of repurchased debt	53,531			118,587
Allocated equity component of repurchased debt	4,121			9,741
Loss on extinguishment of debt, including the write-off of portion of unamortized debt issuance costs	3,454			4,600
Convertible Senior Debentures, Due 2040 [Member]
Debt Instruments [Abstract]
Convertible debt	$ 129			$ 129		126
Issuance date				Nov. 09, 2010
Debt maturity date				Nov. 15, 2040
Cash coupon rate	2.25%			2.25%
Nonconvertible debt borrowing rate at issuance	8.00%			8.00%
Effective conversion rate				81.4200
Effective conversion price (in dollars per share) | $ / shares	$ 12.28			$ 12.28
130% of the conversion price (in dollars per share) | $ / shares				$ 15.96
Convertible senior debentures call date				Nov. 20, 2020
Conversion period before maturity date				3 months
Debt instrument percentage of conversion price				130.00%
Debt instrument percentage of sales price of common stock	98.00%			98.00%
Liability and equity components of convertible debentures [Abstract]
Principal amount of debt	$ 300			$ 300
Convertible Senior Debentures, Due 2041 [Member]
Debt Instruments [Abstract]
Convertible debt	$ 1,065			$ 1,065		6,677
Issuance date				May 13, 2011
Debt maturity date				May 15, 2041
Cash coupon rate	2.25%			2.25%
Nonconvertible debt borrowing rate at issuance	8.375%			8.375%
Effective conversion rate				59.4161
Effective conversion price (in dollars per share) | $ / shares	$ 16.83			$ 16.83
130% of the conversion price (in dollars per share) | $ / shares				$ 21.88
Convertible senior debentures call date				May 20, 2021
Conversion period before maturity date				3 months
Debt instrument percentage of conversion price				130.00%
Debt instrument percentage of sales price of common stock	98.00%			98.00%
Liability and equity components of convertible debentures [Abstract]
Principal amount of debt	$ 2,640			$ 2,640
Interest expense [Abstract]
Principal amount of repurchased debt				14,250
Net carrying value of repurchased debt				5,645
Purchase price of extinguished debt				19,849
Convertible Senior Debentures [Member]
Interest expense [Abstract]
Contractual coupon interest	16		118	76	385
Non-cash amortization of debt discount	8		53	37	170
Other non-cash interest expense (income)	0		(8)	0	(26)
Total interest expense related to the debentures	24		$ 163	113	$ 529
Convertible Debt [Member]
Liability and equity components of convertible debentures [Abstract]
Principal amount of debt	468,284			468,284		617,190
Unamortized discount	(63,745)			(63,745)		(101,259)
Carrying value of liability component	404,539			404,539		515,931
Equity component - net carrying value	67,343			67,343		92,391
Convertible Debt [Member] | Convertible Senior Notes, Due 2025 [Member]
Liability and equity components of convertible debentures [Abstract]
Principal amount of debt	465,344			465,344		600,000
Unamortized discount	(61,999)			(61,999)		(90,872)
Carrying value of liability component	403,345			403,345		509,128
Equity component - net carrying value	66,127			66,127		85,262
Convertible Debt [Member] | Convertible Senior Debentures [Member]
Liability and equity components of convertible debentures [Abstract]
Principal amount of debt	2,940			2,940		17,190
Unamortized discount	(1,746)			(1,746)		(10,387)
Carrying value of liability component	1,194			1,194		6,803
Equity component - net carrying value	$ 1,216			$ 1,216		$ 7,129