Investments (Maturities of Marketable Securities) (Details) - USD ($) $ in Thousands	Dec. 26, 2015	Dec. 27, 2014
Investments [Abstract]
Amortized Cost, Due within one year	$ 9,775
Fair Value, Due within one year	9,839
Amortized Cost, Due after one year through five years	52,426
Fair Value, Due after one year through five years	53,285
Amortized Cost, Due after five years through ten years	20,146
Fair Value, Due after five years through ten years	20,625
Amortized Cost, Equity securities	1,198
Fair Value, Equity securities	7,880
Available-for-sale Securities, Amortized Cost, Total	83,545	$ 65,759
Available-for-sale Securities, Fair Value, Total	$ 91,629	$ 73,959