ACQUISITIONS AND DIVESTITURES - Pro Well Acquisition (Details) - USD ($) $ in Thousands			1 Months Ended
	Sep. 30, 2019	Nov. 20, 2018	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Less: identified assets acquired and liabilities assumed
Goodwill	$ 266,934			$ 273,801	$ 273,421
Well Chemical Services Acquisition
Consideration transferred
Cash paid	10,400
Total consideration transferred	10,400
Less: identified assets acquired and liabilities assumed
Inventory	6,287
Property and equipment	3,713
Intangible assets	500
Current liabilities	(100)
Total identifiable net assets acquired	10,400
Fair value allocated to net assets acquired	$ 10,400
Pro Well Acquisition
Consideration transferred
Cash paid		$ 11,754
Total consideration transferred		11,754	$ 11,800
Less: identified assets acquired and liabilities assumed
Working capital		1,051
Property and equipment		6,588
Total identifiable net assets acquired		10,639
Goodwill		1,115
Fair value allocated to net assets acquired		11,754
Initial payment		12,400
Pro Well Acquisition | Customer relationships
Less: identified assets acquired and liabilities assumed
Intangible assets		$ 3,000