Cash, Cash Equivalents, and Investments - Summary of Cash, Cash Equivalents and Held-to-Maturity Investments by Type (Detail) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	$ 31,688,313	$ 37,807,749
Gross Unrealized Gains	8,339
Gross Unrealized Losses	(39)	(1,488)
Fair Value	31,696,613	37,806,261
Cash and Money Market Funds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	17,091,149	36,126,791
Fair Value	17,091,149	36,126,791
State and Municipal Obligations [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	11,869,005
Gross Unrealized Gains	8,231
Gross Unrealized Losses	(9)
Fair Value	11,877,227
Corporate Bonds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	1,001,384	958
Gross Unrealized Gains	106
Fair Value	1,001,490	958
Certificates of Deposit [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	1,726,775	1,680,000
Gross Unrealized Gains	2
Gross Unrealized Losses	(30)	(1,488)
Fair Value	$ 1,726,747	$ 1,678,512