OTHER COMPREHENSIVE INCOME (LOSS) (Details) - Summary of Other Comprehensive Income - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2019	Mar. 31, 2018
Other Comprehensive Income (Loss), before Tax [Abstract]
Foreign currency translation adjustments	$ 2,885		$ 19,714		$ (2,851)	$ 18,425
Pension and other defined benefit plans	201		376		472	14,620
Cash flow hedges	(264)		616		(107)	746
Total other comprehensive income (loss)	2,822		20,706		(2,486)	33,791
Other Comprehensive Income (Loss), Tax [Abstract]
Pension and other defined benefit plans	(17)		(129)		(104)	(4,814)
Cash flow hedges	75		(176)		20	(218)
Total other comprehensive income (loss)	58		(305)		(84)	(5,032)
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation adjustments	2,885		19,714		(2,851)	18,425
Pension and other defined benefit plans	184		247		368	9,806
Cash flow hedges	(189)		440		(87)	528
Total other comprehensive income (loss), net of taxes	$ 2,880	$ (5,450)	$ 20,401	$ 8,358	$ (2,570)	$ 28,759

Amount before tax, after reclassification adjustments of other comprehensive income (loss).

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