Cash, Cash Equivalents, and Investments (Details) (USD $)	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Summary of cash, cash equivalents and held-to-maturity investments by type
Cost	$ 17,970,019	$ 21,300,733	$ 27,719,405	$ 42,684,241
Gross Unrealized Losses	(4,319)	(3,307)
Gross Unrealized Gains
Fair Value	23,151,963	26,405,615
Cash and money market funds [Member]
Summary of cash, cash equivalents and held-to-maturity investments by type
Cost	17,970,019	21,300,733
Gross Unrealized Losses
Gross Unrealized Gains
Fair Value	17,970,019	21,300,733
Commercial Paper [Member]
Summary of cash, cash equivalents and held-to-maturity investments by type
Cost	3,506,263	5,008,189
Gross Unrealized Losses	(2,831)	(3,238)
Gross Unrealized Gains
Fair Value	3,503,432	5,004,951
Certificates of Deposit [Member]
Summary of cash, cash equivalents and held-to-maturity investments by type
Cost	1,680,000	100,000
Gross Unrealized Losses	(1,488)	(69)
Gross Unrealized Gains
Fair Value	$ 1,678,512	$ 99,931