Stock Plans (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 05, 2020	Jun. 30, 2019	Jul. 05, 2020	Jun. 30, 2019	Dec. 29, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total income tax benefit recognized for stock-based compensation	$ 3,300	$ 3,000	$ 5,500	$ 7,200
Stock-based compensation costs capitalized as part of inventory			500
Proceeds from issuance of common stock under stock plans			10,074	16,554
Share-based Payment Arrangement, Expense	9,603	$ 6,703	$ 12,653	$ 12,801
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date fair value of options		$ 21.95	$ 18.98	$ 22.64
Total intrinsic value of options exercised	7,800	$ 7,900	$ 8,700	$ 16,700
Proceeds from issuance of common stock under stock plans			10,100	16,600
Share-based Payment Arrangement, Expense	800	1,300	1,900	2,700
Total unrecognized compensation cost, net of estimated forfeitures, related to nonvested stock, granted	6,500		$ 6,500
Weighted-average period for recognition of unrecognized compensation cost, years			2 years 2 months 12 days
Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense	2,700	2,800	$ 5,200	5,500
Total unrecognized compensation cost, net of estimated forfeitures, related to nonvested stock, granted	$ 21,200		$ 21,200
Weighted-average period for recognition of unrecognized compensation cost, years			1 year 10 months 24 days
Awards/units outstanding	317,000		317,000		345,000
Number of Shares, Granted			181,000
Weighted-average grant-date fair value of stock granted (per share)			$ 84.13
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period			28,000
Fair value of restricted stock awards vested	$ 1,400	2,000	$ 13,000	11,300
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense	$ 3,300	1,200	$ 2,300	2,400
Awards/units outstanding	31,207		31,207
Number of Shares, Granted			0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period			1,948
Deferred Compensation Share-based Arrangements, Liability, Current and Noncurrent	$ 5,600		$ 5,600
Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense			$ 800	$ 700
Number of Shares, Granted			8,333
Weighted-average grant-date fair value of stock granted (per share)			$ 91.75
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized under plan	5,000,000.0		5,000,000.0
Number of Shares, Granted			27,619	18,562
Weighted-average grant-date fair value of stock granted (per share)			$ 92.72	$ 74.62
Shares available for grant under employee stock purchase plan	800,000		800,000
Performance Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense	$ 2,000	$ 700	$ 2,600	$ 1,500
Awards/units outstanding	121,759		121,759
Number of Shares, Granted			89,986
Weighted-average grant-date fair value of stock granted (per share)			$ 76.76
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period			29,943
2019 Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized under plan					6,250,000