(LOSS) EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Calculation of basic and diluted earnings per share:
Antidilutive shares	3,542,939	2,972,967	3,542,939	2,976,537
Net (loss) income	$ (53,044)	$ 8,068	$ (344,264)	$ 9,468
Net (loss) income attributable to noncontrolling interests	8,746	(1,868)	54,104	(2,133)
Net (loss) income attributable to Select Energy Services, Inc.	(44,298)	6,200	(290,160)	7,335
Add: Reallocation of net loss (income) attributable to noncontrolling interests for the dilutive effect of restricted stock		9		8
Add: Reallocation of net loss (income) attributable to noncontrolling interests for the dilutive effect of stock options		3		2
Net income attributable to Select Energy Services, Inc. - diluted	(44,298)	6,212	(290,160)	7,345
Class A Common Stock
Calculation of basic and diluted earnings per share:
Net (loss) income attributable to Select Energy Services, Inc.	(44,298)	6,200	(290,160)	7,335
Add: Reallocation of net loss (income) attributable to noncontrolling interests for the dilutive effect of restricted stock		9		8
Add: Reallocation of net loss (income) attributable to noncontrolling interests for the dilutive effect of stock options		3		2
Net income attributable to Select Energy Services, Inc. - diluted	$ (44,298)	$ 6,212	$ (290,160)	$ 7,345
Weighted-average shares of common stock outstanding - basic	84,937,043	78,544,502	85,520,935	78,533,761
Dilutive effect of restricted stock		471,542		351,780
Dilutive effect of stock options		150,889		78,353
Dilutive effect of ESPP		102		195
Weighted-average shares of common stock outstanding - diluted	84,937,043	79,167,035	85,520,935	78,964,089
Earnings (loss) per share, Basic (in dollars per share)	$ (0.52)	$ 0.08	$ (3.39)	$ 0.09
Earnings (loss) per share, Diluted (in dollars per share)	$ (0.52)	$ 0.08	$ (3.39)	$ 0.09
Class B Common Stock
Calculation of basic and diluted earnings per share:
Weighted-average shares of common stock outstanding - basic	16,221,101	26,026,843	16,221,101	26,026,843
Weighted-average shares of common stock outstanding - diluted	16,221,101	26,026,843	16,221,101	26,026,843

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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