BUSINESS SEGMENTS AND GEOGRAPHIC INFORMATION - Schedule of Revenues from External Customers and Long-Lived Assets by Country (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Sep. 30, 2025
Segment Reporting [Line Items]
Operating revenues	$ 1,034,856	$ 1,040,924	$ 2,984,244	$ 2,734,265
Property, plant and equipment, net	3,865,332		3,865,332		$ 4,313,074
United States
Segment Reporting [Line Items]
Operating revenues	592,664	659,364	1,738,869	1,876,295
Property, plant and equipment, net	2,240,325		2,240,325		2,503,045
Norway
Segment Reporting [Line Items]
Operating revenues	90,058	82,854	264,771	161,159
Saudi Arabia
Segment Reporting [Line Items]
Operating revenues	74,258	103,752	206,140	201,673
Property, plant and equipment, net	895,012		895,012		971,440
Oman
Segment Reporting [Line Items]
Operating revenues	65,611	45,089	196,475	114,709
Property, plant and equipment, net	389,332		389,332		445,706
Azerbaijan
Segment Reporting [Line Items]
Operating revenues	44,758	38,922	143,390	81,681
Argentina
Segment Reporting [Line Items]
Operating revenues	50,240	39,634	121,767	119,245
Other foreign
Segment Reporting [Line Items]
Operating revenues	117,267	$ 71,309	312,832	$ 179,503
Property, plant and equipment, net	$ 340,663		$ 340,663		$ 392,883