Investments - Short term invesmtments (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Notes to Financial Statements
Custodial trust	$ 946,383	$ 6,275,648
Short-term U.S. treasury bills	0	1,148,395
Certificates of deposit	200,000	200,000
Commercial paper	0	499,383
Bank money market accounts	4,863,646	2,315,307
Bank savings accounts	1,763	1,763
Total short-term investments	$ 6,011,792	$ 10,440,496