LONG-TERM DEBT (Details) - Summary of Long-Term Debt - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017
Debt Instrument [Line Items]
Outstanding Balance	$ 1,106,863		$ 1,106,863		$ 992,401
Debt Instrument, Unamortized Premium	1,396		1,396
less: Current portion, Outstanding Balance	(12,917)		(12,917)		(11,078)
Debt Instrument, Unamortized Premium, Current	0		0
Long-term debt, Outstanding Balance	1,093,946		1,093,946		981,323
Debt Instrument, Unamortized Premium, Noncurrent	1,396		1,396
Original Issuer Discount					(1,177)
less: Current portion, Original Issuer Discount					0
Long-term debt, Original Issuer Discount					(1,177)
Capitalized Fees & Expenses	(16,880)		(16,880)		(12,066)
Long-term debt	1,091,379		1,091,379		979,158
less: Current portion	(12,917)		(12,917)		(11,078)
Long-term debt	1,078,462		1,078,462		968,080
Interest Paid	(15,295)	$ (11,733)	(30,891)	$ (23,136)
Amortization of Debt Discount (Premium)	(68)	(258)	(135)	(1,383)
Amortization of Debt Issuance Costs	1,443	729	2,619	1,496
Interest Expense, Debt	$ (16,806)	$ (12,720)	$ (33,645)	$ (26,015)
Senior notes due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period	5.70%	5.50%	5.70%	5.50%
Outstanding Balance	$ 1,000,000		$ 1,000,000		725,000
Debt Instrument, Unamortized Premium	1,396		1,396
Original Issuer Discount					(1,177)
Capitalized Fees & Expenses	(14,715)		(14,715)		(9,220)
Long-term debt	$ 986,681		$ 986,681		$ 714,603
Coupon Interest Rate	5.25%		5.25%		5.25%
Interest Paid	$ (13,125)	$ (9,515)	$ (26,250)	$ (19,031)
Amortization of Debt Discount (Premium)	(68)	(68)	(135)	(135)
Amortization of Debt Issuance Costs	943	461	1,882	934
Interest Expense, Debt	(14,136)	(10,044)	(28,267)	(20,100)
Revolver due 2021 [Member]
Debt Instrument [Line Items]
Outstanding Balance	14,896		14,896		$ 144,216
Debt Instrument, Unamortized Premium	0		0
Original Issuer Discount					0
Capitalized Fees & Expenses	(1,689)		(1,689)		(1,951)
Long-term debt	13,207		13,207		142,265
Interest Paid	(922)	(1,326)	(2,278)	(1,651)
Amortization of Debt Discount (Premium)	0	0	0	0
Amortization of Debt Issuance Costs	140	150	281	282
Interest Expense, Debt	(1,062)	$ (1,476)	(2,559)	$ (1,933)
Real estate mortgages [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period		2.40%		2.40%
Outstanding Balance	0		0		23,642
Debt Instrument, Unamortized Premium	0		0
Original Issuer Discount					0
Capitalized Fees & Expenses	0		0		(320)
Long-term debt	0		0		23,322
Interest Paid	(166)	$ (158)	(351)	$ (278)
Amortization of Debt Discount (Premium)	0	0	0	0
Amortization of Debt Issuance Costs	303	8	320	10
Interest Expense, Debt	$ (469)	$ (166)	$ (671)	$ (288)
ESOP Loans [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period	4.60%	3.30%	4.30%	4.10%
Outstanding Balance	$ 41,537		$ 41,537		42,675
Debt Instrument, Unamortized Premium	0		0
Original Issuer Discount					0
Capitalized Fees & Expenses	(248)		(248)		(310)
Long-term debt	41,289		41,289		42,365
Interest Paid	(442)	$ (369)	(855)	$ (733)
Amortization of Debt Discount (Premium)	0	0	0	0
Amortization of Debt Issuance Costs	31	38	62	65
Interest Expense, Debt	$ (473)	$ (407)	$ (917)	$ (798)
Capital lease - real estate [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period	5.50%	5.40%	10.70%	5.40%
Outstanding Balance	$ 8,983		$ 8,983		5,312
Debt Instrument, Unamortized Premium	0		0
Original Issuer Discount					0
Capitalized Fees & Expenses	(93)		(93)		(105)
Long-term debt	$ 8,890		$ 8,890		$ 5,207
Coupon Interest Rate	5.00%		5.00%		5.00%
Interest Paid	$ (327)	$ (75)	$ (491)	$ (155)
Amortization of Debt Discount (Premium)	0	0	0	0
Amortization of Debt Issuance Costs	7	6	13	12
Interest Expense, Debt	(334)	(81)	(504)	(167)
Non U.S. lines of credit [Member]
Debt Instrument [Line Items]
Outstanding Balance	2,125		2,125		$ 9,402
Debt Instrument, Unamortized Premium	0		0
Original Issuer Discount					0
Capitalized Fees & Expenses	(24)		(24)		(31)
Long-term debt	2,101		2,101		9,371
Interest Paid	(4)	(21)	(11)	(25)
Amortization of Debt Discount (Premium)	0	0	0	0
Amortization of Debt Issuance Costs	0	7	7	10
Interest Expense, Debt	(4)	(28)	(18)	(35)
Non U.S. term loans [Member]
Debt Instrument [Line Items]
Outstanding Balance	33,277		33,277		35,943
Debt Instrument, Unamortized Premium	0		0
Original Issuer Discount					0
Capitalized Fees & Expenses	(90)		(90)		(108)
Long-term debt	33,187		33,187		35,835
Interest Paid	(330)	(236)	(664)	(458)
Amortization of Debt Discount (Premium)	0	0	0	0
Amortization of Debt Issuance Costs	18	18	51	29
Interest Expense, Debt	(348)	(254)	(715)	(487)
Other long term debt [Member]
Debt Instrument [Line Items]
Outstanding Balance	6,045		6,045		6,211
Debt Instrument, Unamortized Premium	0		0
Original Issuer Discount					0
Capitalized Fees & Expenses	(21)		(21)		(21)
Long-term debt	6,024		6,024		$ 6,190
Interest Paid	(114)	(48)	(229)	(122)
Amortization of Debt Discount (Premium)	0	0	0	0
Amortization of Debt Issuance Costs	1	4	3	6
Interest Expense, Debt	(115)	$ (52)	(232)	$ (128)
Convert. debt due 2017 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period		9.10%		8.90%
Interest Paid	0	$ (167)	0	$ (1,167)
Amortization of Debt Discount (Premium)	0	(190)	0	(1,248)
Amortization of Debt Issuance Costs	0	37	0	148
Interest Expense, Debt	0	(394)	0	(2,563)
Capitalized Interest [Member]
Debt Instrument [Line Items]
Interest Paid	(135)	(182)	(238)	(484)
Amortization of Debt Discount (Premium)	0	0	0	0
Amortization of Debt Issuance Costs	0	0	0	0
Interest Expense, Debt	$ (135)	$ (182)	$ (238)	$ (484)