Long-Term Debt (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 28, 2019	Mar. 30, 2019	Sep. 29, 2018	Jun. 29, 2019	Sep. 28, 2019	Sep. 29, 2018	Dec. 31, 2018
Line of Credit Facility
Line of credit facility, decrease in commitment fee					0.05%
Debt Instruments [Abstract]
Credit facility	$ 0				$ 0		$ 0
Deferred financing costs	(17,650)				(17,650)		(14,968)
Long-term debt	496,262				496,262		494,509
Less current portion	0				0		0
Long-term debt, less current portion	496,262				496,262		494,509
Interest expense [Abstract]
Contractual coupon interest	3,493		$ 4,984		10,510	$ 11,624
Non-cash amortization of debt discount	3,573		4,002		10,558	6,966
Non-cash amortization of deferred financing costs	456		477		1,368	714
Non-cash change in value of derivative liability	(10)		110		(32)	115
Total interest expense related to the debentures	7,512		9,573		22,404	19,419
Allocated liability component of repurchased debt		$ 7,311
Allocated equity component of repurchased debt		15,384
Loss on extinguishment of debt, including the write-off of portion of unamortized debt issuance costs		(1,307)			(1,307)	(17,309)
Convertible Senior Notes, Due 2025 [Member]
Debt Instruments [Abstract]
Convertible debt	$ 505,591				$ 505,591		495,203
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					31.7924
Effective conversion price (in dollars per share)	$ 31.45				$ 31.45
130% of the conversion price (in dollars per share)					$ 40.89
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					$ 0.085
Liability and equity components of convertible debentures [Abstract]
Principal amount of debt	$ 600,000				$ 600,000
Interest expense [Abstract]
Contractual coupon interest	3,375		3,375		10,125	4,088
Non-cash amortization of debt discount	3,520		3,334		10,388	3,890
Non-cash amortization of deferred financing costs	454		454		1,362	605
Non-cash change in value of derivative liability	0		0		0	0
Total interest expense related to the debentures	7,349		7,163		21,875	8,583
Convertible Senior Debentures, Due 2040 [Member]
Debt Instruments [Abstract]
Convertible debt	$ 146				$ 146		539
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					79.6235
Effective conversion price (in dollars per share)	$ 12.56				$ 12.56
130% of the conversion price (in dollars per share)					$ 16.33
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	$ 350				$ 350
Interest expense [Abstract]
Principal amount of repurchased debt		960
Net carrying value of repurchased debt		396
Convertible Senior Debentures, Due 2041 [Member]
Debt Instruments [Abstract]
Convertible debt	$ 8,175				$ 8,175		12,812
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					58.1051
Effective conversion price (in dollars per share)	$ 17.21				$ 17.21
130% of the conversion price (in dollars per share)					$ 22.37
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	$ 20,790				$ 20,790
Interest expense [Abstract]
Principal amount of repurchased debt		12,288
Net carrying value of repurchased debt		4,770
Convertible Senior Debentures, Due 2042 [Member]
Debt Instruments [Abstract]
Convertible debt	0				0		923
Interest expense [Abstract]
Principal amount of repurchased debt		2,168
Net carrying value of repurchased debt		924
Convertible Senior Debentures [Member]
Interest expense [Abstract]
Contractual coupon interest	118		1,609		385	7,536
Non-cash amortization of debt discount	53		668		170	3,076
Non-cash amortization of deferred financing costs	2		23		6	109
Non-cash change in value of derivative liability	(10)		110		(32)	115
Total interest expense related to the debentures	$ 163		$ 2,410		529	$ 10,836
Purchase price of extinguished debt		$ 22,695
Revolving Credit Facility [Member]
Line of Credit Facility
Basis spread on variable rate				1.50%
Commitment fees				0.25%
Incremental revolving commitments				$ 300,000
Line of credit facility, commitment fee percentage				0.25%
Line of credit facility, expiration date				Jun. 05, 2024
Line of credit facility, initiation date	Jun. 05, 2019
Line of credit facility, maximum borrowing capacity	$ 750,000				750,000
Restricted payments (annual limit)	100,000				100,000
Restricted payments (total limit)	300,000				300,000
Restricted payments (rollover limit)	25,000				25,000
Restricted payments pro forma ratio				2.50
Investments pro forma ratio				2.75
Event of default - judgment limit	50,000				50,000
Previous Credit Facility [Member]
Line of Credit Facility
Line of credit facility, expiration date				Dec. 10, 2020
Line of credit facility, maximum borrowing capacity	640,000				640,000
Convertible Debt [Member]
Liability and equity components of convertible debentures [Abstract]
Principal amount of debt	621,140				621,140		636,556
Unamortized discount	(107,238)				(107,238)		(127,149)
Embedded derivative	10				10		70
Carrying value of liability component	513,912				513,912		509,477
Equity component - net carrying value	94,029				94,029		100,354
Convertible Debt [Member] | Convertible Senior Notes, Due 2025 [Member]
Liability and equity components of convertible debentures [Abstract]
Principal amount of debt	600,000				600,000		600,000
Unamortized discount	(94,409)				(94,409)		(104,797)
Embedded derivative	0				0		0
Carrying value of liability component	505,591				505,591		495,203
Equity component - net carrying value	85,262				85,262		85,262
Convertible Debt [Member] | Convertible Senior Debentures [Member]
Liability and equity components of convertible debentures [Abstract]
Principal amount of debt	21,140				21,140		36,556
Unamortized discount	(12,829)				(12,829)		(22,352)
Embedded derivative	10				10		70
Carrying value of liability component	8,321				8,321		14,274
Equity component - net carrying value	$ 8,767				$ 8,767		$ 15,092