Marketable Securities (Maturities of Marketable Securities) (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Marketable Securities [Abstract]
Amortized Cost, Due within one year	$ 7,623
Fair Value, Due within one year	7,667
Amortized Cost, Due after one year through five years	24,811
Fair Value, Due after one year through five years	25,161
Amortized Cost, Due after five years through ten years	22,339
Fair Value, Due after five years through ten years	22,449
Amortized Cost, Equity securities	1,198
Fair Value, Equity securities	9,002
Available-for-sale Securities, Amortized Cost, Total	55,971	$ 58,937
Available-for-sale Securities, Fair Value, Total	$ 64,279	$ 67,171