Cash, Cash Equivalents and Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 29, 2012	Dec. 31, 2011
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	$ 26,695	$ 46,186
Fair value of available-for-sale securities, continuous loss position for twelve month or longer	11,369	17,477
Total fair value of available-for-sale securities, continuous loss position	38,064	63,663
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(12)	(392)
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(1,156)	(1,748)
Available-for-sale securities, total gross unrealized losses	(1,168)	(2,140)
Cost
Due in one year or less, Cost	93,389
Due after one year through ten years, Cost	95,117
Due after ten years, Cost	48,960
Total Cost	237,466
Fair Value
Due in one year or less, Fair Value	93,450
Due after one year through ten years, Fair Value	95,416
Due after ten years, Fair Value	47,804
Total Fair Value	236,670
Corporate bonds
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	9,543	25,438
Total fair value of available-for-sale securities, continuous loss position	9,543	25,438
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(5)	(363)
Available-for-sale securities, total gross unrealized losses	(5)	(363)
Auction rate securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for twelve month or longer	11,369	17,477
Total fair value of available-for-sale securities, continuous loss position	11,369	17,477
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(1,156)	(1,748)
Available-for-sale securities, total gross unrealized losses	(1,156)	(1,748)
Municipal bonds
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	17,152	10,437
Total fair value of available-for-sale securities, continuous loss position	17,152	10,437
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(7)	(12)
Available-for-sale securities, total gross unrealized losses	(7)	(12)
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		5,772
Total fair value of available-for-sale securities, continuous loss position		5,772
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses		(12)
Available-for-sale securities, total gross unrealized losses		(12)
Asset-backed securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months		4,539
Total fair value of available-for-sale securities, continuous loss position		4,539
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses		(5)
Available-for-sale securities, total gross unrealized losses		$ (5)