Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Disclosure Summary Of Significant Accounting Policies Additional Information Detail [Line Items]
Accumulated deficit	$ (79,771,085)		$ (74,137,740)
Cash and cash equivalents	17,514,213	$ 34,771,179	22,604,481	$ 23,222,296
Certificates of deposit	$ 10,440,750		$ 21,818,229
Shares authorized but unissued common stock	111,751,950
Tax benefit attributed to the stock-based compensation expense	$ 0
Unrecognized tax benefits	0
Liability, interest, or penalties related to unrecognized tax benefits	$ 0
Shares excluded from the computation of diluted net loss per share	36,322,254	40,160,947
Intellectual Property
Disclosure Summary Of Significant Accounting Policies Additional Information Detail [Line Items]
Fair value of intellectual property				$ 11,000,000
Computer Equipment
Disclosure Summary Of Significant Accounting Policies Additional Information Detail [Line Items]
Estimated useful lives of property and equipment	3 years
Minimum
Disclosure Summary Of Significant Accounting Policies Additional Information Detail [Line Items]
Estimated useful lives of property and equipment	3 years
Maximum
Disclosure Summary Of Significant Accounting Policies Additional Information Detail [Line Items]
Estimated useful lives of property and equipment	5 years