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	29,878		29,878
Issuance of treasury stock under employee stock plans (in shares)		185
Issuance of treasury stock under employee stock plans	(46,474)	$ 1	(58,861)	12,386
Repurchases of common stock (in shares)		(1,244)
Repurchases of common stock	(493,582)	$ (12)	0	(493,570)
Net income	84,959				84,959
Foreign currency translation adjustments	(2,138)					(2,138)
Ending Balance (in shares) at Dec. 31, 2021		26,509
Ending Balance at Dec. 31, 2021	(538,299)	$ 265	1,208,365	(4,339,039)	2,670,102	(77,992)
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	29,702		29,702
Issuance of treasury stock under employee stock plans (in shares)		180
Issuance of treasury stock under employee stock plans	(70,870)	$ 2	(85,019)	14,147
Repurchases of common stock (in shares)		(179)
Repurchases of common stock	(75,004)	$ (2)		(75,002)
Net income	97,643				97,643
Foreign currency translation adjustments	18,381					18,381
Ending Balance (in shares) at Dec. 31, 2022		25,155
Ending Balance at Dec. 31, 2022	$ (802,095)	$ 252	$ 1,244,271	$ (4,996,624)	$ 3,056,327	$ (106,321)