CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 2,603	$ 2,336
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)	51,620,770	51,071,573
Common stock, shares outstanding (in shares)	50,959,389	50,410,192
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