Condensed Consolidated Statements Of Operations And Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Condensed Consolidated Statements Of Operations And Comprehensive Loss [Abstract]
Revenue
Operating expenses:
General and administrative	5,606	5,675	15,153	16,230
Research and development	6,192	5,038	18,371	12,174
Amortization of intangible assets	166	166	500	499
Total operating expenses	11,964	10,879	34,024	28,903
Other income (expense):
Interest income	218	118	841	311
Total other income (expense)	218	118	841	311
Net loss	(11,746)	(10,761)	(33,183)	(28,592)
Other comprehensive loss:
Unrealized gain (losses) on available-for-sale securities	(14)	(3)	9	48
Comprehensive loss	$ (11,760)	$ (10,764)	$ (33,174)	$ (28,544)
Net loss per share:
Basic and diluted net loss per share	$ (0.57)	$ (0.64)	$ (1.60)	$ (1.69)
Weighted average shares used to compute net loss per common share - basic and diluted	20,774	16,927	20,728	16,883