Basis of Presentation and Summary of Significant Accounting Policies Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 674,284		$ 674,284		$ 426,932	$ 341,003
Gain on investments, net			2,617	$ 12,502
Non-marketable investments	2,900		2,900			$ 3,000
Net income	99,318	$ 81,157	247,352	$ 218,543
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)		$ 1,000