Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Consolidated Balance Sheets
Accounts receivable, reserve for doubtful accounts	$ 36
Accounts receivable, related parties	48	$ 123
Accounts payable, related parties	36	0
Other accrued expenses, related parties	226	170
Deferred revenue, current, related parties	33	1,182
Deferred revenue, net of current portion, related parties	$ 0	$ 1,074
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized shares	120,000,000	120,000,000
Common stock, shares issued	22,369,036	21,707,041
Common stock, shares outstanding	22,369,036	21,707,041