Basis of Presentation and Summary of Significant Accounting Policies Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017	Dec. 31, 2017	Dec. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 574,966		$ 574,966		$ 426,932	$ 341,003
Gain on investments, net			2,136	$ 2,083
Non-marketable investments	3,100		3,100			$ 3,000
Net income	75,149	$ 69,127	148,034	$ 137,386
Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings					2,638
Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings					(8,349)
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings					$ 91,640
Marketable Equity Securities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Gain on investments, net	$ 400		$ 1,400