Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)		1 Months Ended	2 Months Ended	6 Months Ended
	Sep. 18, 2015	Jul. 31, 2016	Aug. 22, 2016	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Disclosure Summary Of Significant Accounting Policies Additional Information Detail [Line Items]
Accumulated deficit				$ (85,100,656)		$ (74,137,740)
Cash and cash equivalents				11,948,858	$ 30,907,953	22,604,481	$ 23,222,296
Proceeds from issuance of common stock and warrants net of offering costs				0	$ 14,599,627
Certificates of deposit				$ 7,967,861		$ 21,818,229
Shares authorized but unissued common stock (in shares)				111,165,945
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 (in shares)				37,120,034	39,032,089
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
California Institute of Regenerative Medicine
Disclosure Summary Of Significant Accounting Policies Additional Information Detail [Line Items]
Proceeds from project initiation payment	$ 4,000,000
Subsequent Event | Maxim Group, LLC
Disclosure Summary Of Significant Accounting Policies Additional Information Detail [Line Items]
Proceeds from issuance of common stock and warrants net of offering costs			$ 7,500,000
Subsequent Event | California Institute of Regenerative Medicine
Disclosure Summary Of Significant Accounting Policies Additional Information Detail [Line Items]
Proceeds from project initiation payment		$ 1,500,000