Cash, Cash Equivalents and Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 29, 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	$ 18,589	$ 13,684
Fair value of available-for-sale securities, continuous loss position for twelve months or longer	10,997	10,632
Total fair value of available-for-sale securities, continuous loss position	29,586	24,316
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(27)	(15)
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(1,428)	(1,793)
Available-for-sale securities, total gross unrealized losses	(1,455)	(1,808)
Cost
Due in one year or less, Cost	168,349
Due after one year through ten years, Cost	84,666
Due after ten years, Cost	45,090
Total Cost	298,105
Fair Value
Due in one year or less, Fair Value	168,456
Due after one year through ten years, Fair Value	84,836
Due after ten years, Fair Value	43,661
Total Fair Value	296,953
Municipal bonds
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	10,662	11,079
Total fair value of available-for-sale securities, continuous loss position	10,662	11,079
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(11)	(11)
Available-for-sale securities, total gross unrealized losses	(11)	(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	10,997	10,632
Total fair value of available-for-sale securities, continuous loss position	10,997	10,632
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(1,428)	(1,793)
Available-for-sale securities, total gross unrealized losses	(1,428)	(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	7,426	2,605
Total fair value of available-for-sale securities, continuous loss position	7,426	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	501
Total fair value of available-for-sale securities, continuous loss position	501
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)