Cash, Cash Equivalents and Investments (Details) (USD $)																												12 Months Ended
	Dec. 29, 2012	Dec. 31, 2011	Dec. 29, 2012 Cash Equivalents:	Dec. 29, 2012 Short-term Investments:	Dec. 31, 2011 Short-term Investments:	Dec. 29, 2012 Long-term Investments:	Dec. 31, 2011 Long-term Investments:	Dec. 29, 2012 U.S. Treasury bills Cash Equivalents:	Dec. 31, 2011 U.S. Treasury bills Short-term Investments:	Dec. 29, 2012 Money market funds Cash Equivalents:	Dec. 31, 2011 Money market funds Cash Equivalents:	Dec. 29, 2012 Corporate bonds Short-term Investments:	Dec. 31, 2011 Corporate bonds Short-term Investments:	Dec. 29, 2012 Municipal bonds Cash Equivalents:	Dec. 29, 2012 Municipal bonds Short-term Investments:	Dec. 31, 2011 Municipal bonds Short-term Investments:	Dec. 29, 2012 Variable-rate demand notes Short-term Investments:	Dec. 31, 2011 Variable-rate demand notes Short-term Investments:	Dec. 29, 2012 Asset-backed securities Short-term Investments:	Dec. 31, 2011 Asset-backed securities Short-term Investments:	Dec. 29, 2012 U.S. government bonds Short-term Investments:	Dec. 31, 2011 U.S. government bonds Short-term Investments:	Dec. 31, 2011 U.S. government agency Short-term Investments:	Dec. 29, 2012 International government bonds Short-term Investments:	Dec. 31, 2011 International government bonds Short-term Investments:	Dec. 29, 2012 Auction rate securities Long-term Investments:	Dec. 31, 2011 Auction rate securities Long-term Investments:	Dec. 29, 2012 Auction rate securities Long-term Investments: Low end of range	Dec. 29, 2012 Auction rate securities Long-term Investments: High end of range	Dec. 31, 2011 Certificates of deposit Short-term Investments:
Cash, Cash Equivalents and Investments
Auction-rate securities guaranteed by the U.S. government	$ 10,500,000
Auction-rate securities privately insured	2,000,000
Auction-rate securities having credit rating 'AAA'	4,500,000
Auction-rate securities having credit rating 'AA'	6,000,000
Auction-rate securities having credit rating 'A'	2,000,000
Cash on hand, Cost	56,690,000	44,113,000
Cash on hand, Fair Value	56,690,000	44,113,000
Cash and cash equivalents, Cost	105,424,000	94,964,000
Cash and cash equivalents, Gross Unrealized Gains	2,000
Cash and cash equivalents, Fair Value	105,426,000	94,964,000
Available-for-sale securities
Long-term investment interest (as a percent)																												0.23%	1.71%
Available-for-sale securities, Cost			48,734,000	176,207,000	212,574,000	12,525,000	19,225,000	25,049,000	8,600,000	22,685,000	50,851,000	59,089,000	75,189,000	1,000,000	45,646,000	56,915,000	41,785,000	41,280,000	15,058,000	5,743,000	12,638,000	2,507,000	19,820,000	1,991,000	950,000	12,525,000	19,225,000			1,570,000
Available-for-sale securities, Gross Unrealized Losses				(12,000)	(392,000)	(1,156,000)	(1,748,000)					(5,000)	(363,000)		(7,000)	(12,000)				(5,000)			(12,000)			(1,156,000)	(1,748,000)
Available-for-sale securities, Gross Unrealized Gains	2,000		2,000	370,000	344,000			1,000		1,000		267,000	234,000		50,000	81,000			11,000	1,000	25,000		28,000	17,000
Available-for-sale securities, Fair Value			$ 48,736,000	$ 176,565,000	$ 212,526,000	$ 11,369,000	$ 17,477,000	$ 25,050,000	$ 8,600,000	$ 22,686,000	$ 50,851,000	$ 59,351,000	$ 75,060,000	$ 1,000,000	$ 45,689,000	$ 56,984,000	$ 41,785,000	$ 41,280,000	$ 15,069,000	$ 5,739,000	$ 12,663,000	$ 2,507,000	$ 19,836,000	$ 2,008,000	$ 950,000	$ 11,369,000	$ 17,477,000			$ 1,570,000