INCOME TAXES - Domestic and Foreign Income (Loss) before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Domestic	$ (458,364)	$ (45,118)	$ 27,436
Foreign	(178,134)	(6,104)	(11,595)
Income (loss) from continuing operations before income taxes	$ (636,498)	$ (51,222)	$ 15,841