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, 2020	Dec. 31, 2019
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Gain on sale of assets	$ 12,336	$ 4,279
Corporate selling, general and administrative costs, corporate depreciation and corporate restructuring charges	39,303	49,808
Operating income (loss) from continuing operations	(93,223)	31,368
Other income (expense)
Interest and dividend income	1,879	2,214
Interest expense	(6,139)	(6,100)
Gain on investment securities	2,924	2,821
Gain on sale of subsidiary	0	14,963
Other	(1,480)	(399)
Total other income (expense)	(2,816)	13,499
Income (loss) from continuing operations before income taxes	(96,039)	44,867
Operating Segment
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Operating income (loss) from continuing operations	(76,558)	60,345
Segment Reconciling Items
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Gain on sale of assets	12,336	4,279
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	$ (29,001)	$ (33,256)