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
	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Operating income	$ 123,468	$ 144,223
Gain on reimbursement of drilling equipment	7,494	15,724
Other gain on sale of assets	2,443	2,379
Corporate selling, general and administrative costs and corporate depreciation	56,577	48,455
Other income (expense)
Interest and dividend income	10,734	4,705
Interest expense	(4,372)	(4,355)
Loss on investment securities	(4,034)	(15,091)
Other	(543)	58
Total unallocated amounts	1,785	(14,683)
Income before income taxes	125,253	129,540
Operating Segments
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Operating income	153,232	160,604
Segment Reconciling Items
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Gain on reimbursement of drilling equipment	7,494	15,724
Other gain on sale of assets	2,443	2,379
Corporate, Non-Segment
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Corporate selling, general and administrative costs and corporate depreciation	$ (39,701)	$ (34,484)