Cash, Cash Equivalents and Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 28, 2014	Dec. 28, 2013
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	$ 24,008	$ 13,684
Fair value of available-for-sale securities, continuous loss position for twelve months or longer	10,993	10,632
Total fair value of available-for-sale securities, continuous loss position	35,001	24,316
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(22)	(15)
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(1,432)	(1,793)
Available-for-sale securities, total gross unrealized losses	(1,454)	(1,808)
Cost
Due in one year or less, Cost	128,339
Due after one year through ten years, Cost	116,829
Due after ten years, Cost	38,895
Total Cost	284,063
Fair Value
Due in one year or less, Fair Value	128,444
Due after one year through ten years, Fair Value	117,062
Due after ten years, Fair Value	37,463
Total Fair Value	282,969
Municipal bonds
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	8,154	11,079
Total fair value of available-for-sale securities, continuous loss position	8,154	11,079
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(2)	(11)
Available-for-sale securities, total gross unrealized losses	(2)	(11)
Auction rate securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for twelve months or longer	10,993	10,632
Total fair value of available-for-sale securities, continuous loss position	10,993	10,632
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(1,432)	(1,793)
Available-for-sale securities, total gross unrealized losses	(1,432)	(1,793)
Corporate bonds
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	10,992	2,605
Total fair value of available-for-sale securities, continuous loss position	10,992	2,605
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(15)	(4)
Available-for-sale securities, total gross unrealized losses	(15)	(4)
Asset-backed securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	2,791
Total fair value of available-for-sale securities, continuous loss position	2,791
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(3)
Available-for-sale securities, total gross unrealized losses	(3)
International government bonds
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	1,471
Total fair value of available-for-sale securities, continuous loss position	1,471
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(1)
Available-for-sale securities, total gross unrealized losses	(1)
U.S. government agency
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	600
Total fair value of available-for-sale securities, continuous loss position	600
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(1)
Available-for-sale securities, total gross unrealized losses	$ (1)