CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Capital In Excess of Par	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock
Beginning balance, common stock (in shares) at Sep. 30, 2019		39,592,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock plans (in shares)		127,000
Issuance of common stock under stock plans		$ 0
Ending balance, common stock (in shares) at Dec. 31, 2019		39,719,000
Balance at beginning of period at Sep. 30, 2019		$ 40	$ 988,980	$ 461,501		$ (23,238)		$ (446,906)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201802Member
Share-based compensation expense			4,763
Exercise of stock options			1,298
Exercise of stock options			0
Issuance of restricted stock under Deposit Share Program			150
Net income	$ 38,549			38,549
Dividends				(12,351)
Cumulative effect of accounting changes					$ 488		$ (488)
Foreign currency translation adjustment	15,851					15,851
Cash flow hedges	4,259					4,259
Beginning balance, treasure stock (in shares) at Sep. 30, 2019								10,491,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock under Share Repurchase Program (in shares)								0
Repurchases of common stock under Share Repurchase Program								$ 0
Repurchase of commons stock - other (in shares)								23,000
Repurchases of common stock - other								$ (2,897)
Ending balance, treasury stock (in shares) at Dec. 31, 2019								10,514,000
Balance at end of period at Dec. 31, 2019	$ 1,029,999	$ 40	995,191	488,187		(3,616)		$ (449,803)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock (in dollars per share)	$ 0.42
Beginning balance, common stock (in shares) at Sep. 30, 2020		39,914,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock plans (in shares)		178,000
Issuance of common stock under stock plans		$ 0
Ending balance, common stock (in shares) at Dec. 31, 2020		40,092,000
Balance at beginning of period at Sep. 30, 2020	$ 1,074,313	$ 40	1,019,803	553,718		(14,104)		$ (485,144)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense			5,851
Exercise of stock options			1,437
Exercise of stock options			3,371
Issuance of restricted stock under Deposit Share Program			215
Net income	31,530			31,530
Dividends				(12,807)
Foreign currency translation adjustment	21,625					21,625
Cash flow hedges	$ (2,386)					(2,386)
Beginning balance, treasure stock (in shares) at Sep. 30, 2020	10,834,000							10,834,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock under Share Repurchase Program (in shares)								62,000
Repurchases of common stock under Share Repurchase Program								$ (9,201)
Repurchase of commons stock - other (in shares)								35,000
Repurchases of common stock - other								$ (5,220)
Ending balance, treasury stock (in shares) at Dec. 31, 2020	10,931,000							10,931,000
Balance at end of period at Dec. 31, 2020	$ 1,108,728	$ 40	$ 1,030,677	$ 572,441		$ 5,135		$ (499,565)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock (in dollars per share)	$ 0.44