Quarterly report pursuant to Section 13 or 15(d)

Investments And Restricted Deposits (Narrative) (Details)

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Investments And Restricted Deposits (Narrative) (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2010
Sep. 30, 2011
Sep. 30, 2010
Investments And Restricted Deposits [Abstract]      
Percentage of investments in securities recorded at fair value that carry a rating by Moody's or S&P of AAA (in hundredths)   36.00%  
Percentage of investments in securities recorded at fair value that carry a rating by Moody's or S&P of AA- or higher (in hundredths)   77.00%  
Percentage of investments in securities recorded at fair value that carry a rating by Moody's or S&P of A- or higher (in hundredths)   99.00%  
Positions from which gross unrealized losses were generated   25  
Total number of positions of available-for-sale securities   410  
Gain from distribution from the Reserve Primary fund     $ 3,287
Impairment of investment 5,531   5,531
Impairment of convertible promissory notes 3,531    
Net realized gain related to sales of fixed income investments     2,472
Investment amortization   $ 7,545 $ 8,380