BUSINESS SEGMENT AND GEOGRAPHIC INFORMATION - Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Reconciliation of segment operating income to income from continuing operations before income taxes
Segment operating income (loss)	$ 111,870	$ 24,814	$ 196,545	$ 54,501
Income from asset sales	11,546	5,255	17,090	10,820
Corporate general and administrative costs and corporate depreciation	(28,270)	(31,233)	(64,200)	(62,876)
Operating income (loss) from continuing operations	95,146	(1,164)	149,435	2,445
Other income (expense)
Interest and dividend income	2,061	1,847	4,512	3,571
Interest expense	(6,167)	(6,028)	(10,888)	(11,801)
Gain (loss) on investment securities	5,878		(36,957)
Other	17	(210)	548	231
Total other income (expense)	1,789	(4,391)	(42,785)	(7,999)
Income (loss) from continuing operations before income taxes	96,935	(5,555)	106,650	(5,554)
Operating segment
Reconciliation of segment operating income to income from continuing operations before income taxes
Segment operating income (loss)	$ 111,870	$ 24,814	$ 196,545	$ 54,501