Investment Securities (Available For Sale Investments) (Details) (USD $)	9 Months Ended		12 Months Ended
	Sep. 27, 2014		Dec. 28, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 150,163,000		$ 128,346,000
Gross Unrealized Gains	627,000	[1]	615,000	[1]
Gross Unrealized Losses	(104,000)	[1]	(47,000)	[1]
Fair Value	150,686,000		128,914,000
Accrued interest on investments	500,000		500,000
Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,166,000		14,629,000
Fair Value	12,166,000		14,629,000
Cash Equivalents [Member] | Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,166,000		14,629,000
Fair Value	12,166,000		14,629,000
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	34,912,000		10,434,000
Gross Unrealized Gains	508,000	[1]	462,000	[1]
Gross Unrealized Losses	(1,000)	[1]	(2,000)	[1]
Fair Value	35,419,000		10,894,000
Short-Term Investments [Member] | Corporate Bonds And Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	32,275,000		7,735,000
Gross Unrealized Gains	439,000	[1]	416,000	[1]
Gross Unrealized Losses	(1,000)	[1]	(2,000)	[1]
Fair Value	32,713,000		8,149,000
Short-Term Investments [Member] | US Treasury And Government Agency Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,514,000		2,499,000
Gross Unrealized Gains	62,000	[1]	44,000	[1]
Fair Value	1,576,000		2,543,000
Short-Term Investments [Member] | Foreign Government And Agency Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,123,000
Gross Unrealized Gains	7,000	[1]
Fair Value	1,130,000
Short-Term Investments [Member] | US States And Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost			200,000
Gross Unrealized Gains			2,000	[1]
Fair Value			202,000
Long-Term Investment Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	103,085,000		103,283,000
Gross Unrealized Gains	119,000	[1]	153,000	[1]
Gross Unrealized Losses	(103,000)	[1]	(45,000)	[1]
Fair Value	103,101,000		103,391,000
Long-Term Investment Securities [Member] | Corporate Bonds And Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	64,242,000		74,583,000
Gross Unrealized Gains	95,000	[1]	121,000	[1]
Gross Unrealized Losses	(76,000)	[1]	(34,000)	[1]
Fair Value	64,261,000		74,670,000
Long-Term Investment Securities [Member] | US Treasury And Government Agency Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	37,204,000		26,421,000
Gross Unrealized Gains	20,000	[1]	30,000	[1]
Gross Unrealized Losses	(25,000)	[1]	(9,000)	[1]
Fair Value	37,199,000		26,442,000
Long-Term Investment Securities [Member] | Foreign Government And Agency Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,409,000		2,049,000
Gross Unrealized Gains	3,000	[1]	1,000	[1]
Gross Unrealized Losses	(2,000)	[1]	(2,000)	[1]
Fair Value	1,410,000		2,048,000
Long-Term Investment Securities [Member] | US States And Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	230,000		230,000
Gross Unrealized Gains	1,000	[1]	1,000	[1]
Fair Value	$ 231,000		$ 231,000

[1] Gross unrealized gains include accrued interest on investments of $0.5 million which are included in the Consolidated Statement of Operations. The remainder of the gross unrealized gains and losses are included in the Consolidated Balance Sheet as Accumulated other comprehensive income (loss).