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, 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)
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)