CONSOLIDATING GUARANTOR AND NON-GUARANTOR FINANCIAL INFORMATION - Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2020	Jun. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 21,831	$ 895	$ 10,612	$ 13,595	$ (1,156)	$ 8,753	$ 33,338	$ 21,192
Net loss from discontinued operations	0			533			0	8,179
Net cash provided by (used in) operating activities:							55,944	14,982
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of property, plant and equipment	(12,232)			(10,376)			(34,751)	(27,794)
Acquired businesses, net of cash acquired							(10,531)	(9,219)
Investment purchase							(130)	(149)
Proceeds from sale of business				(9,500)			0	(9,500)
Insurance payments							0	(10,604)
Proceeds from sale of assets							339	104
Net cash used in investing activities							(45,073)	(57,162)
CASH FLOWS FROM FINANCING ACTIVITIES:
Purchase of shares for treasury							(7,479)	(1,478)
Proceeds from long-term debt							1,230,618	156,800
Payments of long-term debt							(1,205,231)	(108,260)
Contingent consideration for acquired businesses							0	(1,686)
Financing costs							(16,543)	(1,012)
Dividends paid							(10,639)	(10,262)
Other, net							(31)	(197)
Net cash provided by (used in) financing activities							(9,305)	33,905
CASH FLOWS FROM DISCONTINUED OPERATIONS:
Net cash provided by (used) in discontinued operations							(2,481)	(3,874)
Effect of exchange rate changes on cash and equivalents							537	503
NET DECREASE IN CASH AND EQUIVALENTS							(378)	(11,646)
CASH AND EQUIVALENTS AT BEGINNING OF PERIOD			72,377			69,758	72,377	69,758
CASH AND EQUIVALENTS AT END OF PERIOD	71,999			58,112			71,999	58,112
Reportable Legal Entities | Parent Company
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	21,831			13,595			33,338	21,192
Net loss from discontinued operations				0				0
Net cash provided by (used in) operating activities:							(10,683)	(20,805)
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of property, plant and equipment							(306)	(247)
Acquired businesses, net of cash acquired							0	(9,219)
Investment purchase							(130)	(149)
Proceeds from sale of business								(9,500)
Insurance payments								(10,604)
Proceeds from sale of assets							0	0
Net cash used in investing activities							(436)	(29,719)
CASH FLOWS FROM FINANCING ACTIVITIES:
Purchase of shares for treasury							(7,479)	(1,478)
Proceeds from long-term debt							1,224,722	138,541
Payments of long-term debt							(1,171,365)	(75,694)
Contingent consideration for acquired businesses								0
Financing costs							(16,543)	(1,012)
Dividends paid							(10,639)	(10,262)
Other, net							(4,499)	(197)
Net cash provided by (used in) financing activities							14,197	49,898
CASH FLOWS FROM DISCONTINUED OPERATIONS:
Net cash provided by (used) in discontinued operations							0	0
Effect of exchange rate changes on cash and equivalents							0	0
NET DECREASE IN CASH AND EQUIVALENTS							3,078	(626)
CASH AND EQUIVALENTS AT BEGINNING OF PERIOD			1,649			15,976	1,649	15,976
CASH AND EQUIVALENTS AT END OF PERIOD	4,727			15,350			4,727	15,350
Reportable Legal Entities | Guarantor Companies
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	31,542			15,697			63,744	54,400
Net loss from discontinued operations				0				0
Net cash provided by (used in) operating activities:							35,520	24,179
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of property, plant and equipment							(30,497)	(23,221)
Acquired businesses, net of cash acquired							0	0
Investment purchase							0	0
Proceeds from sale of business								0
Insurance payments								0
Proceeds from sale of assets							341	79
Net cash used in investing activities							(30,156)	(23,142)
CASH FLOWS FROM FINANCING ACTIVITIES:
Purchase of shares for treasury							0	0
Proceeds from long-term debt							0	116
Payments of long-term debt							(2,647)	(2,605)
Contingent consideration for acquired businesses								0
Financing costs							0	0
Dividends paid							0	0
Other, net							(7,723)	5,694
Net cash provided by (used in) financing activities							(10,370)	3,205
CASH FLOWS FROM DISCONTINUED OPERATIONS:
Net cash provided by (used) in discontinued operations							0	0
Effect of exchange rate changes on cash and equivalents							(514)	(118)
NET DECREASE IN CASH AND EQUIVALENTS							(5,520)	4,124
CASH AND EQUIVALENTS AT BEGINNING OF PERIOD			25,217			16,353	25,217	16,353
CASH AND EQUIVALENTS AT END OF PERIOD	19,697			20,477			19,697	20,477
Reportable Legal Entities | Non-Guarantor Companies
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	31,649			16,330			63,683	40,829
Net loss from discontinued operations				533				8,179
Net cash provided by (used in) operating activities:							31,107	11,608
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of property, plant and equipment							(3,948)	(4,326)
Acquired businesses, net of cash acquired							(10,531)	0
Investment purchase							0	0
Proceeds from sale of business								0
Insurance payments								0
Proceeds from sale of assets							(2)	25
Net cash used in investing activities							(14,481)	(4,301)
CASH FLOWS FROM FINANCING ACTIVITIES:
Purchase of shares for treasury							0	0
Proceeds from long-term debt							5,896	18,143
Payments of long-term debt							(31,219)	(29,961)
Contingent consideration for acquired businesses								(1,686)
Financing costs							0	0
Dividends paid							0	0
Other, net							12,191	(5,694)
Net cash provided by (used in) financing activities							(13,132)	(19,198)
CASH FLOWS FROM DISCONTINUED OPERATIONS:
Net cash provided by (used) in discontinued operations							(2,481)	(3,874)
Effect of exchange rate changes on cash and equivalents							1,051	621
NET DECREASE IN CASH AND EQUIVALENTS							2,064	(15,144)
CASH AND EQUIVALENTS AT BEGINNING OF PERIOD			45,511			37,429	45,511	37,429
CASH AND EQUIVALENTS AT END OF PERIOD	47,575			22,285			47,575	22,285
Elimination
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	(63,191)			(32,027)			(127,427)	(95,229)
Net loss from discontinued operations				0				0
Net cash provided by (used in) operating activities:							0	0
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of property, plant and equipment							0	0
Acquired businesses, net of cash acquired							0	0
Investment purchase							0	0
Proceeds from sale of business								0
Insurance payments								0
Proceeds from sale of assets							0	0
Net cash used in investing activities							0	0
CASH FLOWS FROM FINANCING ACTIVITIES:
Purchase of shares for treasury							0	0
Proceeds from long-term debt							0	0
Payments of long-term debt							0	0
Contingent consideration for acquired businesses								0
Financing costs							0	0
Dividends paid							0	0
Other, net							0	0
Net cash provided by (used in) financing activities							0	0
CASH FLOWS FROM DISCONTINUED OPERATIONS:
Net cash provided by (used) in discontinued operations							0	0
Effect of exchange rate changes on cash and equivalents							0	0
NET DECREASE IN CASH AND EQUIVALENTS							0	0
CASH AND EQUIVALENTS AT BEGINNING OF PERIOD			$ 0			$ 0	0	0
CASH AND EQUIVALENTS AT END OF PERIOD	$ 0			$ 0			$ 0	$ 0