Marketable Securities (Schedule Of Maturities of Marketable Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 30, 2017
Marketable Securities [Abstract]
Amortized Cost, Due within one year	$ 11,960
Fair Value, Due within one year	11,973
Amortized Cost, Due after one year through five years	22,477
Fair Value, Due after one year through five years	22,583
Amortized Cost, Due after five years through ten years	16,724
Fair Value, Due after five years through ten years	16,584
Amortized Cost, Equity securities	1,198
Fair Value, Equity securities	7,594
Amortized Cost	52,359	$ 55,476
Available-for-sale Securities, Fair Value, Total	$ 58,734	$ 63,665