Grant Revenues - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Jun. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Research And Development Arrangement Contract To Perform For Others [Line Items]
Grant revenues		$ 1,149	$ 1,073	$ 3,381	$ 4,500
Outstanding grant receivable		1,571		1,571		$ 1,697
Deferred revenue		$ 181		181		$ 0
CPRIT
Research And Development Arrangement Contract To Perform For Others [Line Items]
Grant contract term	3 years
Grant contract beginning date	Jun. 01, 2014
Grant contract expiration date	May 31, 2017
CPRIT | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research grant contract amount	$ 19,800			$ 19,800