NEW ACCOUNTING STANDARDS - Balance Sheet Impacts (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Oct. 01, 2018	Sep. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other current liabilities	$ 179,661	$ 164,878	$ 123,303
Retained earnings	178,892	209,132	250,707
Balance without Adoption of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other current liabilities	140,597		123,303
Retained earnings	217,956		$ 250,707
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other current liabilities	39,064	41,575
Retained earnings	$ (39,064)	$ (41,575)