Condensed Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	February 2018 Offering [Member] Common Stock [Member]	February 2018 Offering [Member] Additional Paid-in Capital [Member]	February 2018 Offering [Member]	November 2017 ATM Facility [Member] Common Stock [Member]	November 2017 ATM Facility [Member] Additional Paid-in Capital [Member]	November 2017 ATM Facility [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Total
Balances (in shares) at Dec. 31, 2017							19,503,558
Balances at Dec. 31, 2017							$ 2	$ 102,979	$ (105,581)	$ (2,600)
Stock-based compensation expense								645		645
Issuance of common shares from employee stock purchase plan (in shares)							20,744
Issuance of common shares from employee stock purchase plan								65		65
Issuance of restricted shares (in shares)							22,137
Issuance of restricted shares								108		108
Net loss									(12,669)	(12,669)
Stock offering, net of issuance costs (in shares)	11,500,000			208,277		208,277
Stock offering, net of issuance costs	$ 1	$ 32,224	$ 32,225		$ 1,011	$ 1,011
Balances (in shares) at Mar. 31, 2018							31,254,716
Balances at Mar. 31, 2018							$ 3	137,032	(118,073)	18,962
Cumulative effect adjustment from adoption of new accounting standard – ASC 606									177	177
Balances (in shares) at Dec. 31, 2018							46,363,945
Balances at Dec. 31, 2018							$ 5	160,292	(155,385)	4,912
Stock-based compensation expense								470		470
Issuance of common shares from employee stock purchase plan (in shares)							43,759
Issuance of common shares from employee stock purchase plan								35		35
Issuance of restricted shares (in shares)							27,473
Issuance of restricted shares								25		25
Issuance of common shares in connection with restricted stock award to employee (in shares)							625
Issuance of common shares in connection with restricted stock award to employee								1		1
Net loss									(10,029)	(10,029)
Stock offering, net of issuance costs (in shares)						0
Balances (in shares) at Mar. 31, 2019							46,435,802
Balances at Mar. 31, 2019							$ 5	$ 160,823	$ (165,414)	$ (4,586)