Condensed consolidated statements of stockholders' equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]
Balances at Dec. 31, 2018	$ 72,672		$ 302,759	$ (230,087)
Balances, shares at Dec. 31, 2018		23,537,368
Stock-based compensation	1,078		1,078
Net loss	(2,208)			(2,208)
Balances at Mar. 31, 2019	71,542		303,837	(232,295)
Balances, shares at Mar. 31, 2019		23,537,368
Balances at Dec. 31, 2018	72,672		302,759	(230,087)
Balances, shares at Dec. 31, 2018		23,537,368
Net loss	(2,209)
Balances at Jun. 30, 2019	72,329		304,625	(232,296)
Balances, shares at Jun. 30, 2019		23,537,368
Balances at Mar. 31, 2019	71,542		303,837	(232,295)
Balances, shares at Mar. 31, 2019		23,537,368
Stock-based compensation	788		788
Net loss	(1)			(1)
Balances at Jun. 30, 2019	72,329		304,625	(232,296)
Balances, shares at Jun. 30, 2019		23,537,368
Balances at Dec. 31, 2019	141,687		441,216	(299,529)
Balances, shares at Dec. 31, 2019		37,996,849
Options exercised	3,392		3,392
Options exercised, shares		376,311
Restricted stock units vested, shares		13,000
Stock-based compensation	683		683
Net loss	(8,642)			(8,642)
Balances at Mar. 31, 2020	137,120		445,291	(308,171)
Balances, shares at Mar. 31, 2020		38,386,160
Balances at Dec. 31, 2019	$ 141,687		441,216	(299,529)
Balances, shares at Dec. 31, 2019		37,996,849
Options exercised, shares	475,193
Net loss	$ (18,388)
Balances at Jun. 30, 2020	128,699		446,616	(317,917)
Balances, shares at Jun. 30, 2020		38,486,542
Balances at Mar. 31, 2020	137,120		445,291	(308,171)
Balances, shares at Mar. 31, 2020		38,386,160
Options exercised	303		303
Options exercised, shares		98,882
Restricted stock units vested, shares		1,500
Stock-based compensation	1,022		1,022
Net loss	(9,746)			(9,746)
Balances at Jun. 30, 2020	$ 128,699		$ 446,616	$ (317,917)
Balances, shares at Jun. 30, 2020		38,486,542