Long-Term Debt (Details) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended
	Jul. 04, 2020 USD ($) $ / shares	Apr. 04, 2020 USD ($)	Jun. 29, 2019 USD ($)	Jul. 04, 2020 USD ($) $ / shares	Jun. 29, 2019 USD ($)	Dec. 31, 2019 USD ($)
Debt Instruments [Abstract]
Credit facility	$ 0			$ 0		$ 0
Deferred financing costs	(13,861)			(13,861)		(16,784)
Long-term debt	438,494			438,494		499,147
Less current portion	0			0		0
Long-term debt, less current portion	438,494			438,494		499,147
Interest expense [Abstract]
Contractual coupon interest	3,282		$ 3,494	6,701	$ 7,017
Non-cash amortization of debt discount	3,488		3,495	7,125	6,985
Other non-cash interest expense (income)	435		452	889	890
Total interest expense related to the debentures	7,205		7,441	14,715	14,892
Purchase price of extinguished debt		$ 19,849
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	(1,146)	(2,920)	0	(4,066)	(1,307)
Convertible Senior Notes, Due 2025 [Member]
Debt Instruments [Abstract]
Convertible debt	$ 451,169			$ 451,169		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				31.8470
Effective conversion price (in dollars per share) | $ / shares	$ 31.40			$ 31.40
130% of the conversion price (in dollars per share) | $ / shares				$ 40.82
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	$ 524,230			$ 524,230
Interest expense [Abstract]
Contractual coupon interest	3,266		3,375	6,641	6,750
Non-cash amortization of debt discount	3,479		3,442	7,096	6,868
Other non-cash interest expense (income)	435		454	889	908
Total interest expense related to the debentures	7,180		7,271	14,626	14,526
Principal amount of repurchased debt	75,770			75,770
Net carrying value of repurchased debt	65,056			65,056
Purchase price of extinguished debt	70,676			70,676
Allocated liability component of repurchased debt	65,056			65,056
Allocated equity component of repurchased debt	5,620			5,620
Loss on extinguishment of debt, including the write-off of portion of unamortized debt issuance costs	1,146
Convertible Senior Debentures, Due 2040 [Member]
Debt Instruments [Abstract]
Convertible debt	$ 128			$ 128		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				80.9286
Effective conversion price (in dollars per share) | $ / shares	$ 12.36			$ 12.36
130% of the conversion price (in dollars per share) | $ / shares				$ 16.07
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	$ 1,058			$ 1,058		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				59.0575
Effective conversion price (in dollars per share) | $ / shares	$ 16.93			$ 16.93
130% of the conversion price (in dollars per share) | $ / shares				$ 22.01
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
Convertible Senior Debentures [Member]
Interest expense [Abstract]
Contractual coupon interest	16		119	60	267
Non-cash amortization of debt discount	9		53	29	117
Other non-cash interest expense (income)	0		(2)	0	(18)
Total interest expense related to the debentures	25		$ 170	89	$ 366
Convertible Debt [Member]
Liability and equity components of convertible debentures [Abstract]
Principal amount of debt	527,170			527,170		617,190
Unamortized discount	(74,815)			(74,815)		(101,259)
Carrying value of liability component	452,355			452,355		515,931
Equity component - net carrying value	75,711			75,711		92,391
Convertible Debt [Member] | Convertible Senior Notes, Due 2025 [Member]
Liability and equity components of convertible debentures [Abstract]
Principal amount of debt	524,230			524,230		600,000
Unamortized discount	(73,061)			(73,061)		(90,872)
Carrying value of liability component	451,169			451,169		509,128
Equity component - net carrying value	74,495			74,495		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	(1,754)			(1,754)		(10,387)
Carrying value of liability component	1,186			1,186		6,803
Equity component - net carrying value	$ 1,216			$ 1,216		$ 7,129