Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Accounts receivable, allowance for doubtful accounts	$ 63	$ 14
Shareholders' Equity:
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	33,109,222	29,098,207
Common stock, shares outstanding (in shares)	33,109,222	29,098,207
Series G Convertible Preferred Stock [Member]
Shareholders' Equity:
Preferred stock, shares authorized (in shares)	3,000	3,000
Convertible preferred stock, shares issued (in shares)	225	405
Convertible preferred stock, shares outstanding (in shares)	225	405