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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Gain on sale of assets	$ 4,201	$ 9,960	$ 18,790	$ 27,050
Selling, general and administrative	43,108	46,590	134,894	144,604
Operating loss from continuing operations	(57,584)	(167,874)	(544,757)	(18,439)
Other income (expense)
Interest and dividend income	771	2,349	6,551	6,861
Interest expense	(6,125)	(6,257)	(18,320)	(17,145)
Gain (loss) on investment securities	2,267	(13,271)	(7,325)	(50,228)
Gain on sale of subsidiary	0	0	14,963	0
Other	(2,914)	(1,599)	(3,711)	(1,051)
Total other income (expense)	(6,001)	(18,778)	(7,842)	(61,563)
Loss from continuing operations before income taxes	(63,585)	(186,652)	(552,599)	(80,002)
Operating Segment
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Operating loss from continuing operations	(27,295)	(147,691)	(464,873)	48,855
Segment Reconciling Items
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Gain on sale of assets	4,201	9,960	18,790	27,050
Corporate G&A
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Selling, general and administrative	$ (34,490)	$ (30,143)	$ (98,674)	$ (94,344)