BUSINESS SEGMENTS AND GEOGRAPHIC INFORMATION - Summary of Financial Information of Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 317,364	$ 687,974	$ 1,565,660	$ 2,149,440
Segment Operating Income (Loss)	(57,584)	(167,874)	(544,757)	(18,439)
North America Solutions
Segment Reporting Information [Line Items]
Revenues	254,434	600,831	1,325,076	1,867,253
Offshore Gulf of Mexico
Segment Reporting Information [Line Items]
Revenues	37,494	37,674	110,828	109,167
International Solutions
Segment Reporting Information [Line Items]
Revenues	22,477	46,283	120,189	163,378
Other
Segment Reporting Information [Line Items]
Revenues	2,959	3,186	9,567	9,642
Operating Segment
Segment Reporting Information [Line Items]
Revenues	317,364	687,974	1,565,660	2,149,440
Segment Operating Income (Loss)	(27,295)	(147,691)	(464,873)	48,855
Operating Segment | North America Solutions
Segment Reporting Information [Line Items]
Revenues	254,434	600,831	1,325,076	1,867,253
Segment Operating Income (Loss)	(25,157)	(147,015)	(315,705)	20,514
Operating Segment | Offshore Gulf of Mexico
Segment Reporting Information [Line Items]
Revenues	37,494	37,674	110,828	109,167
Segment Operating Income (Loss)	3,013	5,078	6,022	16,778
Operating Segment | International Solutions
Segment Reporting Information [Line Items]
Revenues	22,477	46,283	120,189	163,378
Segment Operating Income (Loss)	(9,540)	(5,023)	(158,894)	9,575
Operating Segment | Other
Segment Reporting Information [Line Items]
Revenues	13,343	3,186	38,494	9,642
Segment Operating Income (Loss)	4,389	(731)	3,704	1,988
Intersegment
Segment Reporting Information [Line Items]
Revenues	(10,384)	0	(28,927)	0
Segment Operating Income (Loss)	0	0	0	0
Intersegment | North America Solutions
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Intersegment | Offshore Gulf of Mexico
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Intersegment | International Solutions
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Intersegment | Other
Segment Reporting Information [Line Items]
Revenues	$ (10,384)	$ 0	$ (28,927)	$ 0