Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 43	$ 67
Preferred stock, par value ($ per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (shares)	5,000,000	5,000,000
Preferred stock, shares issued (shares)	0	0
Preferred stock, shares outstanding (shares)	0	0
Common stock, par value ($ per share)	$ 0.001	$ 0.001
Common stock, shares authorized (shares)	300,000,000	300,000,000
Common stock, shares issued (shares)	113,299,612	110,525,141
Common stock, shares outstanding (shares)	113,299,612	110,525,141