Cash, Cash Equivalents and Investments (Details) (USD $)																													12 Months Ended
	Dec. 31, 2011	Jan. 01, 2011	Jan. 01, 2011 Cash Equivalents:	Dec. 31, 2011 Short-term Investments:	Jan. 01, 2011 Short-term Investments:	Dec. 31, 2011 Long-term Investments:	Jan. 01, 2011 Long-term Investments:	Dec. 31, 2011 Money market funds Cash Equivalents:	Jan. 01, 2011 Money market funds Cash Equivalents:	Dec. 31, 2011 Corporate bonds Short-term Investments:	Jan. 01, 2011 Corporate bonds Short-term Investments:	Dec. 31, 2011 Municipal bonds Short-term Investments:	Jan. 01, 2011 Municipal bonds Short-term Investments:	Dec. 31, 2011 Variable-rate demand notes Short-term Investments:	Jan. 01, 2011 Variable-rate demand notes Short-term Investments:	Dec. 31, 2011 U.S. government agency Short-term Investments:	Jan. 01, 2011 U.S. government agency Short-term Investments:	Jan. 01, 2011 U.S. Treasury bills Cash Equivalents:	Dec. 31, 2011 U.S. Treasury bills Short-term Investments:	Jan. 01, 2011 U.S. Treasury bills Short-term Investments:	Dec. 31, 2011 Asset-backed securities Short-term Investments:	Dec. 31, 2011 U.S. government bonds Short-term Investments:	Dec. 31, 2011 Certificates of deposit Short-term Investments:	Jan. 01, 2011 Certificates of deposit Short-term Investments:	Dec. 31, 2011 International government bonds Short-term Investments:	Jan. 01, 2011 International government bonds Short-term Investments:	Dec. 31, 2011 Auction rate securities Long-term Investments:	Jan. 01, 2011 Auction rate securities Long-term Investments:	Dec. 31, 2011 Auction rate securities Long-term Investments: Low end of range	Dec. 31, 2011 Auction rate securities Long-term Investments: High end of range	Jan. 01, 2011 Commercial paper Cash Equivalents:	Jan. 01, 2011 Commercial paper Short-term Investments:
Cash, Cash Equivalents and Investments
Auction-rate securities guaranteed by the U.S. government	$ 17,200,000
Auction-rate securities privately insured	2,000,000
Auction-rate securities having credit rating 'AAA'	17,200,000
Auction-rate securities having credit rating 'A'	2,000,000
Cash on hand, Cost	44,113,000	40,644,000
Cash on hand, Fair Value	44,113,000	40,644,000
Cash and cash equivalents, Adjusted Cost	94,964,000	138,566,000
Cash and cash equivalents, Gross Unrealized Gains		1,000
Cash and cash equivalents, Fair Value	94,964,000	138,567,000
Available-for-sale securities
Long-term investment interest																													0.21%	3.14%
Available-for-sale securities, Cost			97,922,000	212,574,000	226,872,000	19,225,000	19,725,000	50,851,000	45,167,000	75,189,000	88,183,000	56,915,000	38,408,000	41,280,000	39,425,000	19,820,000	34,635,000	50,096,000	8,600,000	6,998,000	5,743,000	2,507,000	1,570,000	5,744,000	950,000	10,792,000	19,225,000	19,725,000			2,659,000	2,687,000
Available-for-sale securities, Gross Unrealized Losses				(392,000)	(71,000)	(1,748,000)	(2,225,000)			(363,000)	(46,000)	(12,000)	(18,000)			(12,000)	(5,000)				(5,000)			(2,000)			(1,748,000)	(2,225,000)
Available-for-sale securities, Gross Unrealized Gains			1,000	344,000	494,000					234,000	381,000	81,000	24,000			28,000	50,000	1,000		1,000	1,000					38,000
Available-for-sale securities, Fair Value			$ 97,923,000	$ 212,526,000	$ 227,295,000	$ 17,477,000	$ 17,500,000	$ 50,851,000	$ 45,167,000	$ 75,060,000	$ 88,518,000	$ 56,984,000	$ 38,414,000	$ 41,280,000	$ 39,425,000	$ 19,836,000	$ 34,680,000	$ 50,097,000	$ 8,600,000	$ 6,999,000	$ 5,739,000	$ 2,507,000	$ 1,570,000	$ 5,742,000	$ 950,000	$ 10,830,000	$ 17,477,000	$ 17,500,000			$ 2,659,000	$ 2,687,000