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		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Gain (loss) on sale of assets	$ (18,515)	$ 10,310	$ (6,179)	$ 14,589
Corporate selling, general and administrative costs, corporate depreciation and corporate restructuring charges	39,349	41,978	78,652	91,786
Operating loss from continuing operations	(160,923)	(518,541)	(254,146)	(487,173)
Other income (expense)
Interest and dividend income	4,819	3,566	6,698	5,780
Interest expense	(5,759)	(6,095)	(11,898)	(12,195)
Gain (loss) on investment securities	2,520	(12,413)	5,444	(9,592)
Gain on sale of subsidiary	0	0	0	14,963
Other	(577)	(398)	(2,057)	(797)
Total other income (expense)	1,003	(15,340)	(1,813)	(1,841)
Loss from continuing operations before income taxes	(159,920)	(533,881)	(255,959)	(489,014)
Operating Segment
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Operating loss from continuing operations	(114,819)	(498,079)	(191,377)	(437,578)
Segment Reconciling Items
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Gain (loss) on sale of assets	(18,515)	10,310	(6,179)	14,589
Corporate
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	$ (27,589)	$ (30,772)	$ (56,590)	$ (64,184)