Condensed Consolidated Statements Of Operations And Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Condensed Consolidated Statements Of Operations And Comprehensive Loss [Abstract]
Revenue
Operating expenses:
General and administrative	5,146	5,173	9,547	10,555
Research and development	6,337	3,960	12,179	7,136
Amortization of intangible assets	166	167	333	333
Total operating expenses	11,649	9,300	22,059	18,024
Other income (expense):
Interest income	290	137	622	193
Total other income (expense)	290	137	622	193
Net loss	(11,359)	(9,163)	(21,437)	(17,831)
Other comprehensive loss:
Unrealized gain on available-for-sale securities	20	3	23	51
Comprehensive loss	$ (11,339)	$ (9,160)	$ (21,414)	$ (17,780)
Net loss per share:
Basic and diluted net loss per share	$ (0.55)	$ (0.54)	$ (1.04)	$ (1.06)
Weighted average shares used to compute net loss per common share - basic and diluted	20,728	16,881	20,704	16,861