Cash, Cash Equivalents and Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 29, 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	$ 33,753	$ 26,695
Fair value of available-for-sale securities, continuous loss position for twelve months or longer	10,197	11,369
Total fair value of available-for-sale securities, continuous loss position	43,950	38,064
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(96)	(12)
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(2,228)	(1,156)
Available-for-sale securities, total gross unrealized losses	(2,324)	(1,168)
Cost
Due in one year or less, Cost	163,015
Due after one year through ten years, Cost	64,223
Due after ten years, Cost	62,232
Total Cost	289,470
Fair Value
Due in one year or less, Fair Value	163,035
Due after one year through ten years, Fair Value	64,195
Due after ten years, Fair Value	60,004
Total Fair Value	287,234
Municipal bonds
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	32,598	17,152
Total fair value of available-for-sale securities, continuous loss position	32,598	17,152
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(95)	(7)
Available-for-sale securities, total gross unrealized losses	(95)	(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	10,197	11,369
Total fair value of available-for-sale securities, continuous loss position	10,197	11,369
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(2,228)	(1,156)
Available-for-sale securities, total gross unrealized losses	(2,228)	(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	1,155	9,543
Total fair value of available-for-sale securities, continuous loss position	1,155	9,543
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(1)	(5)
Available-for-sale securities, total gross unrealized losses	$ (1)	$ (5)