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, 2020		29,096
Beginning 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	83,342		83,342
Issuance of treasury stock under employee stock plans (in shares)		321
Issuance of treasury stock under employee stock plans	(74,190)	$ 3	(90,761)	16,568
Repurchases of common stock (in shares)		(1,031)
Repurchases of common stock	(541,205)	$ (10)	(40,000)	(501,195)
Net income	306,364				306,364
Foreign currency translation adjustments	19,445					19,445
Ending Balance (in shares) at Jun. 30, 2021		28,386
Ending Balance at Jun. 30, 2021	124,838	$ 284	1,171,164	(3,482,483)	2,499,423	(63,550)
Beginning Balance (in shares) at Mar. 31, 2021		28,829
Beginning Balance at Mar. 31, 2021	223,303	$ 288	1,181,692	(3,239,109)	2,348,225	(67,793)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	30,004		30,004
Issuance of treasury stock under employee stock plans (in shares)		46
Issuance of treasury stock under employee stock plans	2,073	$ 1	(532)	2,604
Repurchases of common stock (in shares)		(489)
Repurchases of common stock	(285,983)	$ (5)	(40,000)	(245,978)
Net income	151,198				151,198
Foreign currency translation adjustments	4,243					4,243
Ending Balance (in shares) at Jun. 30, 2021		28,386
Ending Balance at Jun. 30, 2021	124,838	$ 284	1,171,164	(3,482,483)	2,499,423	(63,550)
Beginning Balance (in shares) at Sep. 30, 2021		27,568
Beginning 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	86,363		86,363
Issuance of treasury stock under employee stock plans (in shares)		242
Issuance of treasury stock under employee stock plans	(37,910)	$ 3	(54,422)	16,509
Repurchases of common stock (in shares)		(2,558)
Repurchases of common stock	(1,039,984)	$ (26)		(1,039,958)
Net income	282,842				282,842
Foreign currency translation adjustments	(27,841)					(27,841)
Ending Balance (in shares) at Jun. 30, 2022		25,252
Ending Balance at Jun. 30, 2022	(847,472)	$ 253	1,269,289	(4,881,304)	2,867,985	(103,695)
Beginning Balance (in shares) at Mar. 31, 2022		25,982
Beginning Balance at Mar. 31, 2022	(663,416)	$ 260	1,242,280	(4,599,242)	2,774,485	(81,199)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	28,549		28,549
Issuance of treasury stock under employee stock plans (in shares)		5
Issuance of treasury stock under employee stock plans	(1,178)	$ 1	(1,540)	361
Repurchases of common stock (in shares)		(735)
Repurchases of common stock	(282,431)	$ (8)		(282,423)
Net income	93,500				93,500
Foreign currency translation adjustments	(22,496)					(22,496)
Ending Balance (in shares) at Jun. 30, 2022		25,252
Ending Balance at Jun. 30, 2022	$ (847,472)	$ 253	$ 1,269,289	$ (4,881,304)	$ 2,867,985	$ (103,695)