Commitments and Contingencies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies [Line Items]
Security deposit of lease agreement	$ 48,000
Rent expense	$ 400,000	$ 400,000	$ 200,000
Austin, TX | Office Space
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
Austin, TX | Laboratory Space
Commitments and Contingencies [Line Items]
Operating lease agreement, commencement date	2017-02
Operating lease agreement, amended date	2018-10
Operating lease agreement new lease sign date	2017-10
Operating lease new agreement, commencement date	2018-01
Operating lease extension term	Sep. 30, 2021