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Cash Equivalents And Investments (Details) (USD $)
9 Months Ended
Sep. 30, 2011
Dec. 31, 2010
Sep. 30, 2011
Maximum [Member]
years
Sep. 30, 2011
Minimum [Member]
years
Sep. 30, 2011
Money Market Funds [Member]
Dec. 31, 2010
Money Market Funds [Member]
Sep. 30, 2011
Municipal Debt Securities [Member]
Dec. 31, 2010
Municipal Debt Securities [Member]
Sep. 30, 2011
Federal Home Loan Securities [Member]
Dec. 31, 2010
Federal Home Loan Securities [Member]
Dec. 31, 2010
Certificates Of Deposit [Member]
Money market fund at fair value    $ 15,900,000$ 11,700,000     
Short-term investment maturity period, in years  1        
Long-term investment maturity period, in years  61       
Short-Term investments7,209,00017,381,000    7,209,00016,901,000  480,000
Long-Term investments$ 35,019,000$ 27,393,000    $ 20,518,000$ 11,327,000$ 14,501,000$ 16,066,000