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, 2019		28,944
Beginning Balance at Sep. 30, 2019	$ 289,767	$ 289	$ 1,225,365	$ (2,802,450)	$ 1,956,648	$ (90,085)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	93,681		93,681
Issuance of treasury stock under employee stock plans (in shares)		827
Issuance of treasury stock under employee stock plans	(60,644)	$ 9	(100,463)	39,810
Repurchases of common stock (in shares)		(675)
Repurchases of common stock	(235,223)	$ (7)		(235,216)
Net income	236,411				236,411
Foreign currency translation adjustments	7,090					7,090
Ending Balance (in shares) at Sep. 30, 2020		29,096
Ending Balance at Sep. 30, 2020	331,082	$ 291	1,218,583	(2,997,856)	2,193,059	(82,995)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	111,700		111,700
Issuance of treasury stock under employee stock plans (in shares)		349
Issuance of treasury stock under employee stock plans	(70,727)	$ 4	(88,953)	18,222
Repurchases of common stock (in shares)		(1,877)
Repurchases of common stock	(882,222)	$ (19)	(3,982)	(878,221)
Net income	392,084				392,084
Foreign currency translation adjustments	7,141					7,141
Ending Balance (in shares) at Sep. 30, 2021		27,568
Ending Balance at Sep. 30, 2021	(110,942)	$ 276	1,237,348	(3,857,855)	2,585,143	(75,854)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	115,355		115,355
Issuance of treasury stock under employee stock plans (in shares)		264
Issuance of treasury stock under employee stock plans	(34,916)	$ 3	(53,115)	18,196
Repurchases of common stock (in shares)		(2,678)
Repurchases of common stock	(1,096,137)	$ (27)		(1,096,110)
Adjustments to Additional Paid in Capital, Other			0
Net income	373,541				373,541
Foreign currency translation adjustments	(48,848)					(48,848)
Ending Balance (in shares) at Sep. 30, 2022		25,154
Ending Balance at Sep. 30, 2022	$ (801,947)	$ 252	$ 1,299,588	$ (4,935,769)	$ 2,958,684	$ (124,702)