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	56,755		56,755
Issuance of treasury stock under employee stock plans (in shares)		212
Issuance of treasury stock under employee stock plans	(58,456)	$ 2	(75,073)	16,615
Repurchases of common stock (in shares)		(350)
Repurchases of common stock	(191,271)	$ (4)		(191,267)
Net income	199,193				199,193
Foreign currency translation adjustments	24,933					24,933
Ending Balance (in shares) at Mar. 31, 2023		25,016
Ending Balance at Mar. 31, 2023	(770,793)	$ 250	1,281,270	(5,110,421)	3,157,877	(99,769)
Beginning Balance (in shares) at Dec. 31, 2022		25,155
Beginning Balance at Dec. 31, 2022	(802,095)	$ 252	1,244,271	(4,996,624)	3,056,327	(106,321)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	27,053		27,053
Issuance of treasury stock under employee stock plans (in shares)		32
Issuance of treasury stock under employee stock plans	12,414	$ 0	9,946	2,468
Repurchases of common stock (in shares)		(171)
Repurchases of common stock	(116,267)	$ (2)		(116,265)
Net income	101,550				101,550
Foreign currency translation adjustments	6,552					6,552
Ending Balance (in shares) at Mar. 31, 2023		25,016
Ending Balance at Mar. 31, 2023	(770,793)	$ 250	1,281,270	(5,110,421)	3,157,877	(99,769)
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	67,022		67,022
Issuance of treasury stock under employee stock plans (in shares)		205
Issuance of treasury stock under employee stock plans	(118,849)	$ 2	(136,158)	17,307
Repurchases of common stock (in shares)		(222)
Repurchases of common stock	(251,253)	$ (2)		(251,251)
Net income	250,864				250,864
Foreign currency translation adjustments	4,546					4,546
Ending Balance (in shares) at Mar. 31, 2024		24,753
Ending Balance at Mar. 31, 2024	(735,660)	$ 248	1,281,577	(5,558,809)	3,638,923	(97,599)
Beginning Balance (in shares) at Dec. 31, 2023		24,879
Beginning Balance at Dec. 31, 2023	(725,765)	$ 249	1,239,131	(5,380,827)	3,509,124	(93,442)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	35,448		35,448
Issuance of treasury stock under employee stock plans (in shares)		18
Issuance of treasury stock under employee stock plans	8,564	$ 0	6,998	1,566
Repurchases of common stock (in shares)		(144)
Repurchases of common stock	(179,549)	$ (1)		(179,548)
Net income	129,799				129,799
Foreign currency translation adjustments	(4,157)					(4,157)
Ending Balance (in shares) at Mar. 31, 2024		24,753
Ending Balance at Mar. 31, 2024	$ (735,660)	$ 248	$ 1,281,577	$ (5,558,809)	$ 3,638,923	$ (97,599)