Investments - Short term invesmtments (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Notes to Financial Statements
U.S. treasury money market fund	$ 8,542,292	$ 3,357,841
Short-term U.S. treasury bills	0	9,987,804
Bank money market accounts	562,548	947,395
Bank savings accounts	1,763	1,763
Certificates of deposit	1,098,000	1,346,000
Total short-term investments	$ 10,204,603	$ 15,640,803