PROPERTY, PLANT AND EQUIPMENT, INTANGIBLE ASSETS AND GOODWILL - Acquisitions (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill		$ 4,118,756	$ 4,051,082	$ 4,066,575
Stuff Media LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total consideration paid		120,300
Cash consideration paid		74,300
Fixed assets acquired		27,000
Intangible assets acquired		35,200
Goodwill		$ 77,300
Scenario, Forecast | Stuff Media LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration paid	$ 46,000