Fair Value Measurement - Roll Forward for Financial Assets and Liabilities Measured at Fair Value Using Significant Other Observable Inputs (Level 2) (Detail) (Fair Value, Measurements [Member], USD $)	12 Months Ended
	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable debt securities, Ending Balance	$ 23,588,675
Significant Other Observable Inputs (Level 2) [Member] | Bond obligation [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable debt securities, Beginning Balance	125,000
Financial liabilities change settled in earning fair value disclosure	$ (125,000)