Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Open Market Repurchases [Member] Common Stock Outstanding [Member]	Open Market Repurchases [Member] Additional Paid-in Capital [Member]	Open Market Repurchases [Member] AOCI Attributable to Parent [Member]	Open Market Repurchases [Member] Retained Earnings [Member]	Open Market Repurchases [Member] Treasury Stock, Common [Member]	Open Market Repurchases [Member]	Common Stock Outstanding [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Treasury Stock, Common [Member]	Total
Balance (in shares) at Sep. 30, 2023							71,294,247
Balance at Sep. 30, 2023							$ 713	$ 1,156,160	$ (62,426)	$ 1,641,009	$ (200,956)	$ 2,534,500
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes (in shares)							217,947
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes							$ 3	(3)	0	0	0	0
Stock-based compensation							0	8,804	0	0	0	8,804
Net loss							0	0	0	(152,604)	0	(152,604)
Net investment hedge currency translation adjustment, net of tax							0	0	(8,288)		0	(8,288)
Foreign currency translation adjustments							0	0	25,725	0	0	25,725
Changes in unrealized losses on marketable securities, net of tax							0	0	3,276	0	0	3,276
Actuarial loss on pension plans, net of tax							$ 0	0	(15)	0	0	(15)
Balance (in shares) at Mar. 31, 2024							68,075,910
Balance at Mar. 31, 2024							$ 681	999,333	(41,728)	1,488,405	(223,820)	2,222,871
Shares repurchases (in shares)	(3,436,284)
Share repurchases		$ 0	$ 0	$ 0	$ (188,515)	$ (188,527)
Retirement of treasury shares							(23)	(165,628)	0	0	165,651	0
Net loss							$ 0	0	0	(152,604)	0	(152,604)
Balance (in shares) at Dec. 31, 2023							69,180,281
Balance at Dec. 31, 2023							$ 692	1,045,427	(26,784)	1,625,285	(200,956)	2,443,664
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes (in shares)							73,053
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes							$ 1	(1)	0	0	0	0
Stock-based compensation							0	5,602	0	0	0	5,602
Net loss							0	0	0	(136,880)	0	(136,880)
Net investment hedge currency translation adjustment, net of tax							0	0	5,080	0	0	5,080
Foreign currency translation adjustments							0	0	(20,769)	0	0	(20,769)
Changes in unrealized losses on marketable securities, net of tax							0	0	752	0	0	752
Actuarial loss on pension plans, net of tax							$ 0	0	(7)	0	0	(7)
Balance (in shares) at Mar. 31, 2024							68,075,910
Balance at Mar. 31, 2024							$ 681	999,333	(41,728)	1,488,405	(223,820)	2,222,871
Shares repurchases (in shares)	(1,177,424)
Share repurchases		$ 0	$ 0	$ 0	$ (74,559)	$ (74,571)
Retirement of treasury shares							0	(51,695)	0	0	51,695	0
Net loss							$ 0	0	0	(136,880)	0	(136,880)
Balance (in shares) at Sep. 30, 2024							59,031,953
Balance at Sep. 30, 2024							$ 590	505,958	(13,464)	1,476,839	(200,956)	1,768,967
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes (in shares)							205,934
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes							$ 3	1,550	0	0	0	1,553
Stock-based compensation							0	13,453	0	0	0	13,453
Net loss							0	0	0	(53,796)	0	(53,796)
Net investment hedge currency translation adjustment, net of tax							0	0	(5,088)	0	0	(5,088)
Foreign currency translation adjustments							0	0	(23,860)	0	0	(23,860)
Changes in unrealized losses on marketable securities, net of tax							0	0	363	0	0	363
Actuarial loss on pension plans, net of tax							$ 0	0	(100)	0	0	(100)
Balance (in shares) at Mar. 31, 2025							59,237,887
Balance at Mar. 31, 2025							$ 593	520,961	(42,149)	1,423,043	(200,956)	1,701,492
Net loss							$ 0	0	0	(53,796)	0	(53,796)
Balance (in shares) at Dec. 31, 2024							59,153,757
Balance at Dec. 31, 2024							$ 592	511,068	(55,237)	1,463,499	(200,956)	1,718,966
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes (in shares)							84,130
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes							$ 1	1,552	0	0	0	1,553
Stock-based compensation							0	8,341	0	0	0	8,341
Net loss							0	0	0	(40,456)	0	(40,456)
Net investment hedge currency translation adjustment, net of tax							0	0	(10,500)	0	0	(10,500)
Foreign currency translation adjustments							0	0	23,438	0	0	23,438
Changes in unrealized losses on marketable securities, net of tax							0	0	200	0	0	200
Actuarial loss on pension plans, net of tax							$ 0	0	(50)	0	0	(50)
Balance (in shares) at Mar. 31, 2025							59,237,887
Balance at Mar. 31, 2025							$ 593	520,961	(42,149)	1,423,043	(200,956)	1,701,492
Net loss							$ 0	$ 0	$ 0	$ (40,456)	$ 0	$ (40,456)