Grant Revenues - Additional Information (Details) - USD ($)		3 Months Ended		9 Months Ended
	Jun. 01, 2014	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Research And Development Arrangement Contract To Perform For Others [Line Items]
Grant revenues		$ 1,261,000	$ 1,149,000	$ 3,723,000	$ 3,381,000
Outstanding grant receivables		2,452,000		2,452,000		$ 1,215,000
Deferred revenue		$ 50,000		$ 50,000		$ 71,000
CPRIT
Research And Development Arrangement Contract To Perform For Others [Line Items]
Grant contract term	4 years
Grant contract beginning date	Jun. 01, 2014
Grant contract expiration date	May 31, 2018
CPRIT | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research grant contract amount	$ 19,800,000