Cash, Cash Equivalents and Investments (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 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	$ 6,336	$ 46,186
Fair value of available-for-sale securities, continuous loss position for twelve month or longer	11,418	17,477
Total fair value of available-for-sale securities, continuous loss position	17,754	63,663
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(3)	(392)
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(1,107)	(1,748)
Available-for-sale securities, total gross unrealized losses	(1,110)	(2,140)
Cost
Due in one year or less, Cost	115,773
Due after one year through ten years, Cost	85,140
Due after ten years, Cost	30,355
Total Cost	231,268
Fair Value
Due in one year or less, Fair Value	115,842
Due after one year through ten years, Fair Value	85,519
Due after ten years, Fair Value	29,248
Total Fair Value	230,609
Corporate bonds
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale securities, continuous loss position for less than twelve months	1,119	25,438
Total fair value of available-for-sale securities, continuous loss position	1,119	25,438
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(1)	(363)
Available-for-sale securities, total gross unrealized losses	(1)	(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	11,418	17,477
Total fair value of available-for-sale securities, continuous loss position	11,418	17,477
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for 12 months or greater, gross unrealized losses	(1,107)	(1,748)
Available-for-sale securities, total gross unrealized losses	(1,107)	(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	5,217	10,437
Total fair value of available-for-sale securities, continuous loss position	5,217	10,437
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale securities, continuous loss position for less than 12 months, gross unrealized losses	(2)	(12)
Available-for-sale securities, total gross unrealized losses	(2)	(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)