CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts receivable, net of allowance	$ 39	$ 12
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, authorized	10,000,000	10,000,000
Common stock, par value	$ 0.001	$ 0.001
Common stock, authorized	300,000,000	300,000,000
Common stock, issued	55,508,314	45,771,422
Common stock, outstanding	55,508,314	45,771,422
Series A Preferred Stock
Preferred stock, authorized	1,684,375	1,684,375
Preferred stock, issued
Preferred stock, outstanding
Series B Preferred Stock
Preferred stock, authorized	1,580,790	1,580,790
Preferred stock, issued	926,942	926,942
Preferred stock, outstanding	926,942	926,942
Liquidation preference	$ 18,394
Nonvoting Common Stock
Common stock, par value	$ 0.001	$ 0.001
Common stock, authorized	3,553,000	3,553,000
Common stock, issued	896	896
Common stock, outstanding	896	896