Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information (Unaudited)
Operating expenses	$ 6,747	$ 6,682	$ 7,325	$ 6,334	$ 6,088	$ 6,008	$ 6,636	$ 7,639	$ 27,088	$ 26,371
Net loss	$ (6,610)	$ (6,514)	$ (7,131)	$ (6,038)	$ (6,060)	$ (5,679)	$ (6,479)	$ (7,652)	$ (26,293)	$ (25,870)
Net loss per share:
Basic and Diluted (in dollars per share)	$ (0.55)	$ (0.56)	$ (0.62)	$ (0.62)	$ 0.85	$ (0.80)	$ (1.98)	$ (2.88)	$ (2.35)	$ (5.12)
Weighted-average common shares outstanding used in net loss per share:
Basic and Diluted (in shares)	11,950,674	11,624,232	11,505,542	9,686,224	7,115,507	7,103,841	3,272,877	2,655,584	11,199,057	5,054,823