CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' DEFICIT - 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, 2024		24,392
Beginning 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	40,654		40,654
Issuance of treasury stock under employee stock plans (in shares)		130
Issuance of treasury stock under employee stock plans	(192,864)	$ 1	(205,398)	12,533
Repurchases of common stock (in shares)		(79)
Repurchases of common stock	(159,749)	$ (1)		(159,748)
Net income	152,528				152,528
Foreign currency translation adjustments	(16,054)					(16,054)
Ending balance (in shares) at Dec. 31, 2024		24,443
Ending balance at Dec. 31, 2024	(1,138,164)	$ 244	1,201,828	(6,285,951)	4,053,398	(107,683)
Beginning balance (in shares) at Sep. 30, 2025		23,764
Beginning balance at Sep. 30, 2025	(1,745,784)	$ 238	1,331,120	(7,537,908)	4,552,816	(92,050)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	44,269		44,269
Issuance of treasury stock under employee stock plans (in shares)		94
Issuance of treasury stock under employee stock plans	(102,247)	$ 1	(113,371)	11,123
Repurchases of common stock (in shares)		(95)
Repurchases of common stock	(162,678)	$ (1)		(162,677)
Net income	158,373				158,373
Foreign currency translation adjustments	(67)					(67)
Ending balance (in shares) at Dec. 31, 2025		23,763
Ending balance at Dec. 31, 2025	$ (1,808,134)	$ 238	$ 1,262,018	$ (7,689,462)	$ 4,711,189	$ (92,117)