Investments (Details) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Investments    
Cost $ 8,025,940 $ 7,691,541
Gross Unrealized Gains 2,626  
Gross Unrealized Losses 63,045 89,337
Fair Value 7,965,521 7,602,204
Cost    
Less than 1 year 2,503,313  
1 to 3 years 4,901,553  
3 to 5 years 621,074  
Fair Value    
Less than 1 year 2,495,449  
1 to 3 years 4,863,174  
3 to 5 years 606,898  
U.S. corporations    
Investments    
Cost 6,814,295 6,176,341
Gross Unrealized Gains 385  
Gross Unrealized Losses 52,072 68,381
Fair Value 6,762,608 6,107,960
International corporations    
Investments    
Cost 1,211,645 1,515,200
Gross Unrealized Gains 2,241  
Gross Unrealized Losses 10,973 20,956
Fair Value $ 1,202,913 $ 1,494,244