Annual report pursuant to Section 13 and 15(d)

Fair Value of Financial Instruments - Hierarchy Table (Details)

v3.3.1.900
Fair Value of Financial Instruments - Hierarchy Table (Details) - USD ($)
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Fair value    
Charges for other-than-temporary declines in fair value of investments $ 0 $ 0
Available-for-sale investment securities with contractual maturity date of more than one but less than two years 22,500,000  
Cash    
Fair value    
Adjusted Cost 20,672,737 7,141,548
Fair Value 20,672,737 7,141,548
Cash and Cash Equivalents | Cash    
Fair value    
Fair Value 20,672,737 7,141,548
Total    
Fair value    
Adjusted Cost 172,843,869 106,922,981
Unrealized Gains 361 258
Unrealized Losses (206,217) (19,040)
Fair Value 172,638,013 106,904,199
Total | Cash and Cash Equivalents    
Fair value    
Fair Value 46,773,566 36,205,559
Total | Marketable Securities.    
Fair value    
Fair Value 125,864,447 70,698,640
Level 1    
Fair value    
Adjusted Cost 16,121,691 99,781,433
Unrealized Gains 92 258
Unrealized Losses (1,434) (19,040)
Fair Value 16,120,349 99,762,651
Level 1 | Cash and Cash Equivalents    
Fair value    
Fair Value 4,100,829 29,064,011
Level 1 | Marketable Securities.    
Fair value    
Fair Value 12,019,520 70,698,640
Level 1 | Money market mutual funds    
Fair value    
Adjusted Cost 4,100,829 29,064,011
Fair Value 4,100,829 29,064,011
Level 1 | Money market mutual funds | Cash and Cash Equivalents    
Fair value    
Fair Value 4,100,829 29,064,011
Level 1 | U.S. Treasury securities    
Fair value    
Adjusted Cost 12,020,862 70,717,422
Unrealized Gains 92 258
Unrealized Losses (1,434) (19,040)
Fair Value 12,019,520 70,698,640
Level 1 | U.S. Treasury securities | Marketable Securities.    
Fair value    
Fair Value 12,019,520 70,698,640
Level 2    
Fair value    
Adjusted Cost 136,049,441  
Unrealized Gains 269  
Unrealized Losses (204,783)  
Fair Value 135,844,927  
Level 2 | Cash and Cash Equivalents    
Fair value    
Fair Value 22,000,000  
Level 2 | Marketable Securities.    
Fair value    
Fair Value 113,844,927  
Level 2 | Repurchase agreements    
Fair value    
Adjusted Cost 22,000,000  
Fair Value 22,000,000  
Level 2 | Repurchase agreements | Cash and Cash Equivalents    
Fair value    
Fair Value 22,000,000  
Level 2 | U.S. government agency securities    
Fair value    
Adjusted Cost 114,049,441  
Unrealized Gains 269  
Unrealized Losses (204,783)  
Fair Value 113,844,927  
Level 2 | U.S. government agency securities | Marketable Securities.    
Fair value    
Fair Value 113,844,927  
Level 3    
Fair value    
Transfers into Level 3 0 0
Transfers out of Level 3 $ 0 $ 0