Revenue - Additional Information (Details) - USD ($)	1 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2019	Aug. 31, 2017	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Revenue from grant				$ 165,000
Grant funds received returned amount					$ 2,663,000
Deferred revenue balance						$ 2,663,000
Revenue recognized included in contract liability at beginning of period				200,000
CPRIT | Non-commercial License Agreement
Disaggregation Of Revenue [Line Items]
Maximum paid percentage of grant award proceeds until which revenue share is payable			400.00%
Royalty payments			$ 0	$ 0
CPRIT | Grant
Disaggregation Of Revenue [Line Items]
Revenue from grant		$ 9,000,000
Period of grant		3 years
Percentage of obligation of grant funds used		50.00%
Cost incurred to obtain or fulfill the contract		$ 0
Grant funds received returned amount	$ 2,600,000
Interest relating to grant funds returned	100,000
Deferred revenue balance	$ 0				$ 0