Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Reserves for accounts receivable	$ 1,567	$ 1,646
Common stock, par value	$ 0.002	$ 0.002
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	171,537,000	170,820,000
Common stock, shares outstanding	171,537,000	170,820,000