Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Condensed Consolidated Balance Sheets
Accounts receivable, allowance for doubtful accounts	$ 4,077	$ 3,725
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	1,600,000,000	1,600,000,000
Common stock, shares issued	152,565,218	150,578,451
Common stock, shares outstanding	152,515,918	150,529,151
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	4,569,233	6,194,233
Preferred stock, shares outstanding	4,569,233	6,194,233
Common stock held in treasury at cost (in shares)	49,300	49,300