Marketable Securities (Maturities of Marketable Securities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 27, 2014	Dec. 28, 2013
Marketable Securities [Abstract]
Amortized Cost, Due within one year	$ 1,875
Fair Value, Due within one year	1,912
Amortized Cost, Due after one year through five years	46,613
Fair Value, Due after one year through five years	47,740
Amortized Cost, Due after five years through ten years	16,073
Fair Value, Due after five years through ten years	16,426
Amortized Cost, Equity securities	1,198
Fair Value, Equity securities	7,881
Amortized Cost, Total	65,759	56,401
Available-for-sale Securities, Fair Value, Total	$ 73,959	$ 63,093