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	57,814		57,814
Issuance of treasury stock under employee stock plans (in shares)		237
Issuance of treasury stock under employee stock plans	(36,732)	$ 2	(52,882)	16,148
Repurchases of common stock (in shares)		(1,823)
Repurchases of common stock	(757,553)	$ (18)	0	(757,535)
Net income	189,342				189,342
Foreign currency translation adjustments	(5,345)					(5,345)
Ending Balance (in shares) at Mar. 31, 2022		25,982
Ending Balance at Mar. 31, 2022	(663,416)	$ 260	1,242,280	(4,599,242)	2,774,485	(81,199)
Beginning Balance (in shares) at Dec. 31, 2021		26,509
Beginning Balance at Dec. 31, 2021	(538,299)	$ 265	1,208,365	(4,339,039)	2,670,102	(77,992)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	27,936		27,936
Issuance of treasury stock under employee stock plans (in shares)		52
Issuance of treasury stock under employee stock plans	9,742	$ 1	5,979	3,762
Repurchases of common stock (in shares)		(579)
Repurchases of common stock	(263,971)	$ (6)	0	(263,965)
Net income	104,383				104,383
Foreign currency translation adjustments	(3,207)					(3,207)
Ending Balance (in shares) at Mar. 31, 2022		25,982
Ending Balance at Mar. 31, 2022	(663,416)	$ 260	1,242,280	(4,599,242)	2,774,485	(81,199)
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)