Commitments and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Aug. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Commitments and Contingencies [Line Items]
Security deposit of lease agreement		$ 39,000
Rent expense		$ 151,000	$ 140,000	$ 17,000
University Research Agreement
Commitments and Contingencies [Line Items]
Research agreement expiration date		Aug. 31, 2017
Payments pursuant to research agreements	$ 375,000	$ 832,000	$ 563,000	$ 386,000
Austin, TX
Commitments and Contingencies [Line Items]
Operating lease agreement, commencement date		2015-01
Operating lease agreement, amended date		2016-09
Operating lease agreement, expiration date		Dec. 31, 2020
Tenant improvements allowances on both the original space and expansion space		$ 200,000