EARNINGS (LOSS) PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Calculation of basic and diluted earnings per share:
Antidilutive shares	3,777,228	2,980,567
Net income	$ (291,220)	$ 1,400
Net income attributable to noncontrolling interests	45,358	(265)
Net (loss) income attributable to Select Energy Services, Inc.	(245,862)	1,135
Add: Reallocation of net income attributable to noncontrolling interests for the dilutive effect of restricted stock		1
Net income attributable to Select Energy Services, Inc. - diluted	(245,862)	1,136
Class A Common Stock
Calculation of basic and diluted earnings per share:
Net (loss) income attributable to Select Energy Services, Inc.	(245,862)	1,135
Add: Reallocation of net income attributable to noncontrolling interests for the dilutive effect of restricted stock		1
Net income attributable to Select Energy Services, Inc. - diluted	$ (245,862)	$ 1,136
Weighted-average shares of common stock outstanding - basic	86,104,925	78,523,768
Dilutive effect of restricted stock		209,811
Dilutive effect of stock options		34,488
Dilutive effect of ESPP		94
Weighted-average shares of common stock outstanding - diluted	86,104,925	78,768,161
Earnings (loss) per share, Basic (in dollars per share)	$ (2.86)	$ 0.01
Earnings (loss) per share, Diluted (in dollars per share)	$ (2.86)	$ 0.01
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
Weighted-average shares of common stock outstanding - diluted	16,221,101	26,026,843