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	82,358		82,358
Issuance of treasury stock under employee stock plans (in shares)		151
Issuance of treasury stock under employee stock plans	(182,468)	$ 2	(197,146)	14,676
Repurchases of common stock (in shares)		(191)
Repurchases of common stock	(366,759)	$ (2)		(366,757)
Net income	315,143				315,143
Foreign currency translation adjustments	(9,647)					(9,647)
Ending balance (in shares) at Mar. 31, 2025		24,352
Ending balance at Mar. 31, 2025	(1,124,052)	$ 244	1,251,784	(6,490,817)	4,216,013	(101,276)
Beginning balance (in shares) at Dec. 31, 2024		24,443
Beginning balance at Dec. 31, 2024	(1,138,164)	$ 244	1,201,828	(6,285,951)	4,053,398	(107,683)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	41,704		41,704
Issuance of treasury stock under employee stock plans (in shares)		21
Issuance of treasury stock under employee stock plans	10,396	$ 1	8,252	2,143
Repurchases of common stock (in shares)		(112)
Repurchases of common stock	(207,010)	$ (1)		(207,009)
Net income	162,615				162,615
Foreign currency translation adjustments	6,407					6,407
Ending balance (in shares) at Mar. 31, 2025		24,352
Ending balance at Mar. 31, 2025	(1,124,052)	$ 244	1,251,784	(6,490,817)	4,216,013	(101,276)
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	89,579		89,579
Issuance of treasury stock under employee stock plans (in shares)		110
Issuance of treasury stock under employee stock plans	(90,832)	$ 1	(103,955)	13,122
Repurchases of common stock (in shares)		(579)
Repurchases of common stock	(773,949)	$ (6)		(773,943)
Net income	422,831				422,831
Foreign currency translation adjustments	(3,495)					(3,495)
Ending balance (in shares) at Mar. 31, 2026		23,295
Ending balance at Mar. 31, 2026	(2,101,650)	$ 233	1,316,744	(8,298,729)	4,975,647	(95,545)
Beginning balance (in shares) at Dec. 31, 2025		23,763
Beginning balance at Dec. 31, 2025	(1,808,134)	$ 238	1,262,018	(7,689,462)	4,711,189	(92,117)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	45,310		45,310
Issuance of treasury stock under employee stock plans (in shares)		16
Issuance of treasury stock under employee stock plans	11,415		9,416	1,999
Repurchases of common stock (in shares)		(484)
Repurchases of common stock	(611,271)	$ (5)		(611,266)
Net income	264,458				264,458
Foreign currency translation adjustments	(3,428)					(3,428)
Ending balance (in shares) at Mar. 31, 2026		23,295
Ending balance at Mar. 31, 2026	$ (2,101,650)	$ 233	$ 1,316,744	$ (8,298,729)	$ 4,975,647	$ (95,545)