CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock Share Repurchase Program, Accelerated Share Repurchase Programs	Common Stock Share Repurchase Program, Open Market Share Repurchase Programs	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)	Treasury Stock Share Repurchase Program, Accelerated Share Repurchase Programs	Treasury Stock Share Repurchase Program, Open Market Share Repurchase Programs	Treasury Stock	Share Repurchase Program, Accelerated Share Repurchase Programs	Share Repurchase Program, Open Market Share Repurchase Programs	Total
Beginning Balance at Sep. 30, 2020			$ 873	$ 1,942,850	$ 21,919	$ (551,072)			$ (200,956)			$ 1,213,614
Beginning Balance (in shares) at Sep. 30, 2020			87,293,710
Increase (Decrease) in Stockholders' Equity
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes			$ 5	5,806								5,811
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes (in shares)			515,212
Stock-based compensation				27,456								27,456
Common stock dividends declared						(29,726)						(29,726)
Foreign currency translation adjustments					(2,922)							(2,922)
Actuarial gain (loss) arising in the year, net of tax					354							354
Net Income (Loss)						110,747						110,747
Ending Balance at Sep. 30, 2021			$ 878	1,976,112	19,351	(470,051)			(200,956)			1,325,334
Ending Balance (in shares) at Sep. 30, 2021			87,808,922
Increase (Decrease) in Stockholders' Equity
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes			$ 7	5,239								5,246
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes (in shares)			673,203
Stock-based compensation				10,666								10,666
Common stock dividends declared						(7,494)						(7,494)
Net investment hedge currency translation adjustment, net of tax / Unrealized gain on derivative asset, net of tax					93,020							93,020
Foreign currency translation reclassification adjustments included in income from discontinued operations					(16,567)							(16,567)
Foreign currency translation adjustments					(169,266)							(169,266)
Changes in unrealized gains (losses) on marketable securities, net of tax					(10,908)							(10,908)
Actuarial gain (loss) arising in the year, net of tax					454							454
Net Income (Loss)						2,132,859						2,132,859
Other						42						42
Ending Balance at Sep. 30, 2022			$ 885	1,992,017	(83,916)	1,655,356			(200,956)			$ 3,363,386
Ending Balance (in shares) at Sep. 30, 2022			88,482,125									75,020,256
Increase (Decrease) in Stockholders' Equity
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes			$ 3	(1,371)								$ (1,368)
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes (in shares)			267,133
Share repurchases							$ (501,637)	$ (342,400)		$ (501,637)	$ (342,400)
Share repurchases (in shares)	(10,072,055)	(7,382,956)
Retirement of treasury shares			$ (175)	(843,862)					844,037
Stock-based compensation				9,376								9,376
Net investment hedge currency translation adjustment, net of tax / Unrealized gain on derivative asset, net of tax					(61,533)							(61,533)
Foreign currency translation adjustments					77,246							77,246
Changes in unrealized gains (losses) on marketable securities, net of tax					5,774							5,774
Actuarial gain (loss) arising in the year, net of tax					3							3
Net Income (Loss)						(14,257)						(14,257)
Other						(90)						(90)
Ending Balance at Sep. 30, 2023			$ 713	$ 1,156,160	$ (62,426)	$ 1,641,009			$ (200,956)			$ 2,534,500
Ending Balance (in shares) at Sep. 30, 2023			71,294,247									57,832,378