Basis of Presentation and Summary of Significant Accounting Policies Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017	Dec. 31, 2017	Dec. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 499,817		$ 426,932	$ 341,003
Gain on investments, net	(1,123)	$ (1,228)
Non-marketable investments	3,000
Net income	72,885	$ 68,259
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	$ (1,000)