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Organization and Summary of Significant Accounting Policies Risks - concentration Revenue and Acct Rec, trading and H-T-M amounts (Details) (USD $)
Mar. 31, 2013
Dec. 31, 2012
Mar. 31, 2012
Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]        
Trading Securities $ 0 $ 0    
Cash and cash equivalents 69,817,000 62,313,000 201,420,000 191,762,000
Held-to-maturity Securities, Fair Value 0 0    
Money Market Funds [Member]
       
Schedule of Available-for-sale Securities [Line Items]        
Cash and cash equivalents 40,368,000 38,892,000    
Cash and Cash Equivalents, Fair Value Disclosure   $ 38,891,000