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RESTRUCTURING CHARGES - Summary of Restructuring and Other Similar Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost and Reserve [Line Items]
Employee termination benefits			$ 18,978
Stock-based compensation benefit			(3,483)
Total restructuring charges	$ 15,495	$ 0	15,495	$ 0
Corporate G&A
Restructuring Cost and Reserve [Line Items]
Employee termination benefits			4,629
Stock-based compensation benefit			(197)
Total restructuring charges			4,432
North America Solutions \| Operating Segment
Restructuring Cost and Reserve [Line Items]
Employee termination benefits			10,273
Stock-based compensation benefit			(3,036)
Total restructuring charges			7,237
Offshore Gulf of Mexico \| Operating Segment
Restructuring Cost and Reserve [Line Items]
Employee termination benefits			1,440
Stock-based compensation benefit			(178)
Total restructuring charges			1,262
International Solutions \| Operating Segment
Restructuring Cost and Reserve [Line Items]
Employee termination benefits			2,308
Stock-based compensation benefit			(11)
Total restructuring charges			2,297
Other \| Operating Segment
Restructuring Cost and Reserve [Line Items]
Employee termination benefits			328
Stock-based compensation benefit			(61)
Total restructuring charges			$ 267