CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Allowance for doubtful accounts	$ 1,907	$ 1,550
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	400,000,000	400,000,000
Common stock, shares issued (in shares)	51,100,591	51,002,234
Common stock, shares outstanding (in shares)	50,439,210	50,340,853
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	1	1
Preferred stock, shares outstanding (in shares)	1	1
Treasury stock (in shares)	661,381	661,381
Treasury Stock
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001