CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 23, 2016	Sep. 22, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 8,685	$ 8,602	$ 6,196			$ 3,208
Common stock, par value (in dollars per share)	$ 0.000001	$ 0.000001
Common stock, shares authorized (in shares)	200,000,000	200,000,000		200,000,000	500,000,000
Common stock, shares issued (in shares)	81,996,839	83,724,916
Common stock, shares outstanding (in shares)	81,996,839	83,724,916