SHAREHOLDERS' EQUITY (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Changes in shareholder's equity
Beginning Balance			$ 1,019,696
Net earnings	$ 16,583	$ 15,404	28,107	$ 28,222
Ending Balance	1,021,173	990,660	1,021,173	990,660
Common Stock
Changes in shareholder's equity
Beginning Balance	307	306	307	306
Ending Balance	307	306	307	306
Additional Paid-In Capital
Changes in shareholder's equity
Beginning Balance	296,277	294,735	297,644	293,682
Stock plans	2,076	1,061	709	2,114
Ending Balance	298,353	295,796	298,353	295,796
Retained Earnings
Changes in shareholder's equity
Beginning Balance	840,434	786,563	830,989	775,829
Net earnings	16,583	15,404	28,107	28,222
Dividends paid	(2,071)	(2,083)	(4,150)	(4,167)
Ending Balance	854,946	799,884	854,946	799,884
Accumulated Other Comprehensive Income (Loss)
Changes in shareholder's equity
Beginning Balance	(4,661)	1,692	(2,161)	(3,657)
Foreign currency translation	(2,811)	116	(5,311)	5,465
Ending Balance	(7,472)	1,808	(7,472)	1,808
Treasury Stock
Changes in shareholder's equity
Beginning Balance	(117,080)	(107,134)	(107,083)	(107,134)
Issued under stock plans	(7,881)		(17,878)
Ending Balance	$ (124,961)	$ (107,134)	$ (124,961)	$ (107,134)