Balance Sheet Components (Schedule Of Available-For-Sale Short-Term) (Details) - USD ($) $ in Thousands	Oct. 01, 2017	Dec. 31, 2016
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Cost	$ 124,321	$ 124,017
Unrealized Gain	0	9
Unrealized Loss	(72)	(40)
Estimated Fair Value	124,249	123,986
U.S. Treasuries [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Cost	124,159	123,869
Unrealized Gain	0	9
Unrealized Loss	(72)	(40)
Estimated Fair Value	124,087	123,838
Certificates Of Deposits [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Cost	162	148
Unrealized Gain	0	0
Unrealized Loss	0	0
Estimated Fair Value	$ 162	$ 148