CONSOLIDATED STATEMENTS 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	123,847		123,847
Issuance of treasury stock under employee stock plans (in shares)		231
Issuance of treasury stock under employee stock plans	(54,475)	$ 2	(72,722)	18,245
Repurchases of common stock (in shares)		(615)
Repurchases of common stock	(407,347)	$ (6)		(407,341)
Net income	429,375				429,375
Foreign currency translation adjustments	22,557					22,557
Ending Balance (in shares) at Sep. 30, 2023		24,770
Ending 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	149,439		149,439
Issuance of treasury stock under employee stock plans (in shares)		228
Issuance of treasury stock under employee stock plans	(114,183)	$ 2	(133,580)	19,395
Repurchases of common stock (in shares)		(606)
Repurchases of common stock	(833,272)	$ (6)		(833,266)
Net income	512,811				512,811
Foreign currency translation adjustments	10,516					10,516
Ending Balance (in shares) at Sep. 30, 2024		24,392
Ending Balance at Sep. 30, 2024	(962,679)	$ 244	1,366,572	(6,138,736)	3,900,870	(91,629)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	156,667		156,667
Issuance of treasury stock under employee stock plans (in shares)		205
Issuance of treasury stock under employee stock plans	(171,770)	$ 2	(192,119)	20,347
Repurchases of common stock (in shares)		(833)
Repurchases of common stock	(1,419,527)	$ (8)		(1,419,519)
Net income	651,946				651,946
Foreign currency translation adjustments	(421)					(421)
Ending Balance (in shares) at Sep. 30, 2025		23,764
Ending Balance at Sep. 30, 2025	$ (1,745,784)	$ 238	$ 1,331,120	$ (7,537,908)	$ 4,552,816	$ (92,050)