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	89,750		89,750
Issuance of treasury stock under employee stock plans (in shares)		218
Issuance of treasury stock under employee stock plans	(59,829)	$ 2	(76,948)	17,117
Repurchases of common stock (in shares)		(480)
Repurchases of common stock	(289,906)	$ (5)		(289,901)
Net income	327,951				327,951
Foreign currency translation adjustments	30,005					30,005
Ending Balance (in shares) at Jun. 30, 2023		24,892
Ending Balance at Jun. 30, 2023	(703,976)	$ 249	1,312,390	(5,208,553)	3,286,635	(94,697)
Beginning Balance (in shares) at Mar. 31, 2023		25,016
Beginning Balance at Mar. 31, 2023	(770,793)	$ 250	1,281,270	(5,110,421)	3,157,877	(99,769)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	32,995		32,995
Issuance of treasury stock under employee stock plans (in shares)		6
Issuance of treasury stock under employee stock plans	(1,373)	$ 0	(1,875)	502
Repurchases of common stock (in shares)		(130)
Repurchases of common stock	(98,635)	$ (1)		(98,634)
Net income	128,758				128,758
Foreign currency translation adjustments	5,072					5,072
Ending Balance (in shares) at Jun. 30, 2023		24,892
Ending Balance at Jun. 30, 2023	(703,976)	$ 249	1,312,390	(5,208,553)	3,286,635	(94,697)
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	109,457		109,457
Issuance of treasury stock under employee stock plans (in shares)		212
Issuance of treasury stock under employee stock plans	(121,543)	$ 2	(139,453)	17,908
Repurchases of common stock (in shares)		(418)
Repurchases of common stock	(506,798)	$ (4)		(506,794)
Net income	377,120				377,120
Foreign currency translation adjustments	448					448
Ending Balance (in shares) at Jun. 30, 2024		24,564
Ending Balance at Jun. 30, 2024	(829,306)	$ 246	1,320,717	(5,813,751)	3,765,179	(101,697)
Beginning Balance (in shares) at Mar. 31, 2024		24,753
Beginning Balance at Mar. 31, 2024	(735,660)	$ 248	1,281,577	(5,558,809)	3,638,923	(97,599)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	42,435		42,435
Issuance of treasury stock under employee stock plans (in shares)		7
Issuance of treasury stock under employee stock plans	(2,694)	$ 0	(3,295)	601
Repurchases of common stock (in shares)		(196)
Repurchases of common stock	(255,545)	$ (2)		(255,543)
Net income	126,256				126,256
Foreign currency translation adjustments	(4,098)					(4,098)
Ending Balance (in shares) at Jun. 30, 2024		24,564
Ending Balance at Jun. 30, 2024	$ (829,306)	$ 246	$ 1,320,717	$ (5,813,751)	$ 3,765,179	$ (101,697)