Investments - Short term invesmtments (Details) - USD ($)	Mar. 31, 2016	Dec. 31, 2015
Notes to Financial Statements
Short-term U.S. treasury bills	$ 4,994,799	$ 9,987,804
U.S. treasury money market fund	4,720,402	3,357,841
Certificates of deposit	450,000	1,346,000
Bank money market accounts	1,122,427	947,395
Bank savings accounts	1,763	1,763
Total short-term investments	$ 11,289,391	$ 15,640,803

Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 1
-Subparagraph g
-Article 7

Name:	us-gaap_ShortTermInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant