Annual report pursuant to Section 13 and 15(d)

Balance Sheets and Statements of Operations Details (Textual) (Details)

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Balance Sheets and Statements of Operations Details (Textual) (Details) (USD $)
12 Months Ended
Dec. 31, 2012
securities
Dec. 31, 2011
securities
Feb. 28, 2011
Dec. 31, 2010
Dec. 31, 2009
Balance Sheets Details [Abstract]          
Cash and cash equivalents $ 32,003,000 $ 25,762,000   $ 72,396,000 $ 31,785,000
Money market funds 24,800,000 18,900,000      
Cash with major financial institutions 7,200,000 6,900,000      
Number of months in an unrealized loss position (months)   12 months      
Number of marketable securities (securities) 0 14      
Maximum unrealized loss position period (months) Less than 12 months        
Aggregated unrealized loss amount   46,000      
Fair value of marketable securities   18,500,000      
Exiting leasehold improvements, net     $ 2,300,000    
Maximum extended useful life 5 years