CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets
Accounts receivable allowance	$ 1,186	$ 1,434
Prepaid and other assets allowance	45	644
Employee loans current allowance	0	0
Noncurrent assets
Employee loans long-term allowance	0	0
Other long-term assets allowance	$ 140	$ 132
Stockholders' equity
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	160,000,000	160,000,000
Common stock, shares issued	53,003,420	51,117,422
Common stock, shares outstanding	52,983,685	51,097,687