CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance (in shares) at Sep. 30, 2022		25,154
Beginning Balance at Sep. 30, 2022	$ (801,947)	$ 252	$ 1,299,588	$ (4,935,769)	$ 2,958,684	$ (124,702)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	29,702		29,702
Issuance of treasury stock under employee stock plans (in shares)		180
Issuance of treasury stock under employee stock plans	(70,870)	$ 2	(85,019)	14,147
Repurchases of common stock (in shares)		(179)
Repurchases of common stock	(75,004)	$ (2)		(75,002)
Net income	97,643				97,643
Foreign currency translation adjustments	18,381					18,381
Ending Balance (in shares) at Dec. 31, 2022		25,155
Ending Balance at Dec. 31, 2022	(802,095)	$ 252	1,244,271	(4,996,624)	3,056,327	(106,321)
Beginning Balance (in shares) at Sep. 30, 2023		24,770
Beginning Balance at Sep. 30, 2023	(687,990)	$ 248	1,350,713	(5,324,865)	3,388,059	(102,145)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	31,574		31,574
Issuance of treasury stock under employee stock plans (in shares)		187
Issuance of treasury stock under employee stock plans	(127,413)	$ 2	(143,156)	15,741
Repurchases of common stock (in shares)		(78)
Repurchases of common stock	(71,704)	$ (1)		(71,703)
Net income	121,065				121,065
Foreign currency translation adjustments	8,703					8,703
Ending Balance (in shares) at Dec. 31, 2023		24,879
Ending Balance at Dec. 31, 2023	$ (725,765)	$ 249	$ 1,239,131	$ (5,380,827)	$ 3,509,124	$ (93,442)