BUSINESS SEGMENTS AND GEOGRAPHIC INFORMATION - Reconciliation of Segment Operating Income (Loss) to Income from Continuing Operations before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Operating income (loss) from continuing operations	$ 148,742	$ 33,722	$ 468,170	$ (31,506)
Gain on reimbursement of drilling equipment	10,642	9,895	37,940	21,597
Other gain (loss) on sale of assets	(4,504)	3,075	394	2,762
Corporate selling, general and administrative costs, corporate depreciation and corporate restructuring charges	49,271	44,933	150,581	135,699
Other income (expense)
Interest and dividend income	10,748	5,313	20,508	11,301
Interest expense	(4,324)	(4,372)	(12,918)	(14,876)
Gain (loss) on investment securities	(18,538)	(14,310)	6,123	55,684
Loss on extinguishment of debt	0	0	0	(60,083)
Other	(685)	(1,148)	(2,088)	(2,166)
Total unallocated amounts	(12,799)	(14,517)	11,625	(10,140)
Income (loss) from continuing operations before income taxes	135,943	19,205	479,795	(41,646)
Operating Segments
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Operating income (loss) from continuing operations	179,381	56,500	537,332	50,632
Segment Reconciling Items
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Gain on reimbursement of drilling equipment	10,642	9,895	37,940	21,597
Other gain (loss) on sale of assets	(4,504)	3,075	394	2,762
Corporate, Non-Segment
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Corporate selling, general and administrative costs, corporate depreciation and corporate restructuring charges	$ (36,777)	$ (35,748)	$ (107,496)	$ (106,497)