Cash, Cash Equivalents and Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 30, 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	$ 25,507	$ 26,695
Fair value of available-for-sale securities, continuous loss position for twelve month or longer	11,189	11,369
Total fair value of available-for-sale securities, continuous loss position	36,696	38,064
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(19)	(12)
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(1,261)	(1,156)
Available-for-sale securities, total gross unrealized losses	(1,280)	(1,168)
Cost
Due in one year or less, Cost	121,784
Due after one year through ten years, Cost	99,419
Due after ten years, Cost	67,935
Total Cost	289,138
Fair Value
Due in one year or less, Fair Value	121,854
Due after one year through ten years, Fair Value	99,698
Due after ten years, Fair Value	66,674
Total Fair Value	288,226
Municipal bonds
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	13,196	17,152
Total fair value of available-for-sale securities, continuous loss position	13,196	17,152
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(10)	(7)
Available-for-sale securities, total gross unrealized losses	(10)	(7)
Auction rate securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for twelve month or longer	11,189	11,369
Total fair value of available-for-sale securities, continuous loss position	11,189	11,369
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(1,261)	(1,156)
Available-for-sale securities, total gross unrealized losses	(1,261)	(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	6,989	9,543
Total fair value of available-for-sale securities, continuous loss position	6,989	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)
Asset-backed securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	5,322
Total fair value of available-for-sale securities, continuous loss position	5,322
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(2)
Available-for-sale securities, total gross unrealized losses	$ (2)