Marketable Securities (Schedule Of Maturities of Marketable Securities) (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Marketable Securities [Abstract]
Amortized Cost, Due within one year	$ 12,535
Fair Value, Due within one year	12,585
Amortized Cost, Due after one year through five years	22,421
Fair Value, Due after one year through five years	22,655
Amortized Cost, Due after five years through ten years	19,322
Fair Value, Due after five years through ten years	19,593
Amortized Cost, Equity securities	1,198
Fair Value, Equity securities	8,832
Amortized Cost	55,476	$ 58,937
Available-for-sale Securities, Fair Value, Total	$ 63,665	$ 67,171