Investments - Short term invesmtments (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Notes to Financial Statements
U.S. treasury money market fund	$ 3,357,841	$ 1,450,451
Short-term U.S. treasury bills	9,987,804	69,968,988
Bank money market accounts	947,395	838,207
Bank savings accounts	1,763	1,762
Certificates of deposit	1,346,000	0
Total short-term investments	$ 15,640,803	$ 72,259,408

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

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant