Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Condensed Consolidated Balance Sheets
Accounts receivable, allowance for doubtful accounts	$ 8,348	$ 4,359
Accumulated depreciation on property, plant and equipment	$ 167,376	$ 154,060
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	152,782,534	152,692,140
Common stock, shares outstanding	150,007,085	150,142,955
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	4,569,233
Preferred stock, shares outstanding	4,569,233	4,569,233
Common stock held in treasury at cost (in shares)	2,787,147	2,549,185