Cash, Cash Equivalents and Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 28, 2013	Dec. 29, 2012
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	$ 18,169	$ 26,695
Fair value of available-for-sale securities, continuous loss position for twelve months or longer	10,671	11,369
Total fair value of available-for-sale securities, continuous loss position	28,840	38,064
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(20)	(12)
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(1,754)	(1,156)
Available-for-sale securities, total gross unrealized losses	(1,774)	(1,168)
Cost
Due in one year or less, Cost	125,011
Due after one year through ten years, Cost	77,491
Due after ten years, Cost	40,550
Total Cost	243,052
Fair Value
Due in one year or less, Fair Value	125,053
Due after one year through ten years, Fair Value	77,618
Due after ten years, Fair Value	38,796
Total Fair Value	241,467
Municipal bonds
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	14,453	17,152
Total fair value of available-for-sale securities, continuous loss position	14,453	17,152
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(13)	(7)
Available-for-sale securities, total gross unrealized losses	(13)	(7)
Auction rate securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for twelve months or longer	10,671	11,369
Total fair value of available-for-sale securities, continuous loss position	10,671	11,369
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(1,754)	(1,156)
Available-for-sale securities, total gross unrealized losses	(1,754)	(1,156)
Corporate bonds
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	3,716	9,543
Total fair value of available-for-sale securities, continuous loss position	3,716	9,543
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(7)	(5)
Available-for-sale securities, total gross unrealized losses	$ (7)	$ (5)