XML 75 R39.htm IDEA: XBRL DOCUMENT v2.4.0.8
Fair Value Measurement of Assets and Liabilities - Additional Information (Detail) (USD $)
6 Months Ended
Jun. 30, 2013
Dec. 31, 2012
Fair Value Measurements Of Financial Instruments [Line Items]    
Short-term investments $ 61,725,464 $ 87,379,121
Proceeds from sales of available-for-sale 141,200,000  
Net impact of sale of investments 518,713  
Reclassification of other comprehensive income to net income 871,702  
Auction Rate Securities [Member]
   
Fair Value Measurements Of Financial Instruments [Line Items]    
Investments 0 0
Collateralized Debt Obligations [Member]
   
Fair Value Measurements Of Financial Instruments [Line Items]    
Investments 0 0
Structured Investment Vehicles [Member]
   
Fair Value Measurements Of Financial Instruments [Line Items]    
Investments $ 0 $ 0