Cash, Cash Equivalents, and Investments (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of cash, cash equivalents and held-to-maturity investments by type
Cost	$ 36,126,791	$ 21,300,733	$ 42,684,241	$ 45,505,049
Gross Unrealized Gains
Gross Unrealized Losses	(1,488)	(3,307)
Fair Value	37,806,261	26,405,615
Cash and money market funds [Member]
Summary of cash, cash equivalents and held-to-maturity investments by type
Cost	36,126,791	21,300,733
Gross Unrealized Gains
Fair Value	36,126,791	21,300,733
Corporate bonds [Member]
Summary of cash, cash equivalents and held-to-maturity investments by type
Cost	958	5,008,189
Gross Unrealized Gains
Gross Unrealized Losses		(3,238)
Fair Value	958	5,004,951
Certificate of deposit [Member]
Summary of cash, cash equivalents and held-to-maturity investments by type
Cost	1,680,000	100,000
Gross Unrealized Gains
Gross Unrealized Losses	(1,488)	(69)
Fair Value	$ 1,678,512	$ 99,931