CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)	Treasury Stock	Total
Beginning Balance at Sep. 30, 2022	$ 885	$ 1,992,017	$ (83,916)	$ 1,655,356	$ (200,956)	$ 3,363,386
Beginning Balance (in shares) at Sep. 30, 2022	88,482,125
Increase (Decrease) in Stockholders' Equity
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes		1,573			(4,629)	(3,056)
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes (in shares)	210,711
Share repurchases					(500,000)	(500,000)
Share repurchases (in shares)	(6,090,134)
Retirement of treasury shares	$ (59)	(504,568)			504,629	2
Stock-based compensation		6,096				6,096
Net Income (Loss)				(16,162)		(16,162)
Net investment hedge currency translation adjustment, net of tax			(70,260)			(70,260)
Foreign currency translation adjustments			111,264			111,264
Changes in unrealized gains on marketable securities, net of tax			4,042			4,042
Other				(85)		(85)
Ending Balance at Mar. 31, 2023	$ 826	1,495,118	(38,870)	1,639,109	(200,956)	2,895,227
Ending Balance (in shares) at Mar. 31, 2023	82,602,702
Beginning Balance at Dec. 31, 2022	$ 824	1,489,554	(62,074)	1,644,041	(200,956)	2,871,389
Beginning Balance (in shares) at Dec. 31, 2022	82,515,917
Increase (Decrease) in Stockholders' Equity
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes		1,573				1,573
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes (in shares)	86,785
Retirement of treasury shares	$ 2					2
Stock-based compensation		3,991				3,991
Net Income (Loss)				(4,927)		(4,927)
Net investment hedge currency translation adjustment, net of tax			(13,133)			(13,133)
Foreign currency translation adjustments			33,850			33,850
Changes in unrealized gains on marketable securities, net of tax			2,487			2,487
Other				(5)		(5)
Ending Balance at Mar. 31, 2023	$ 826	1,495,118	(38,870)	1,639,109	(200,956)	2,895,227
Ending Balance (in shares) at Mar. 31, 2023	82,602,702
Beginning Balance at Sep. 30, 2023	$ 713	1,156,160	(62,426)	1,641,009	(200,956)	$ 2,534,500
Beginning Balance (in shares) at Sep. 30, 2023	71,294,247					57,832,378
Increase (Decrease) in Stockholders' Equity
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes	$ 3	(3)
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes (in shares)	217,947
Share repurchases	$ (12)				(188,515)	$ (188,527)
Share repurchases (in shares)	(3,436,284)
Retirement of treasury shares	$ (23)	(165,628)			165,651
Stock-based compensation		8,804				8,804
Net Income (Loss)				(152,604)		(152,604)
Net investment hedge currency translation adjustment, net of tax			(8,288)			(8,288)
Foreign currency translation adjustments			25,725			25,725
Changes in unrealized gains on marketable securities, net of tax			3,276			3,276
Actuarial loss on pension plans, net of tax			(15)			(15)
Ending Balance at Mar. 31, 2024	$ 681	999,333	(41,728)	1,488,405	(223,820)	$ 2,222,871
Ending Balance (in shares) at Mar. 31, 2024	68,075,910					54,614,041
Beginning Balance at Dec. 31, 2023	$ 692	1,045,427	(26,784)	1,625,285	(200,956)	$ 2,443,664
Beginning Balance (in shares) at Dec. 31, 2023	69,180,281
Increase (Decrease) in Stockholders' Equity
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes	$ 1	(1)
Shares issued under restricted stock and purchase plans, net of shares withheld for employee taxes (in shares)	73,053
Share repurchases	$ (12)				(74,559)	(74,571)
Share repurchases (in shares)	(1,177,424)
Retirement of treasury shares		(51,695)			51,695
Stock-based compensation		5,602				5,602
Net Income (Loss)				(136,880)		(136,880)
Net investment hedge currency translation adjustment, net of tax			5,080			5,080
Foreign currency translation adjustments			(20,769)			(20,769)
Changes in unrealized gains on marketable securities, net of tax			752			752
Actuarial loss on pension plans, net of tax			(7)			(7)
Ending Balance at Mar. 31, 2024	$ 681	$ 999,333	$ (41,728)	$ 1,488,405	$ (223,820)	$ 2,222,871
Ending Balance (in shares) at Mar. 31, 2024	68,075,910					54,614,041