Consolidated Statements of Stockholder's Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Loss
Beginning balance at Sep. 30, 2020	$ 1,438,248	$ 1,161	$ 1,602,728	$ (62,267)	$ (103,374)
Beginning balance (in shares) at Sep. 30, 2020		116,125,000
Common stock issued for employee stock-based awards	0	$ 15	(15)
Common stock issued for employee stock-based awards (in shares)		1,490,000
Shares surrendered by employees to pay taxes related to stock-based awards	(53,077)	$ (4)	(53,073)
Shares surrendered by employees to pay taxes related to stock-based awards (in shares)		(466,000)
Common stock issued for employee stock purchase plan	21,575	$ 2	21,573
Common stock issued for employee stock purchase plan (in shares)		240,000
Compensation expense from stock-based awards	177,289		177,289
Net Income (Loss)	476,923			476,923
Gain (loss) on net investment hedges, net of tax	1,248				1,248
Repurchases of common stock	$ (30,000)	$ (2)	(29,998)
Repurchases of common stock (in shares)	(230,000)	(226,000)
Foreign currency translation adjustment	$ 1,613				1,613
Unrealized loss on marketable securities, net of tax	(307)				(307)
Change in pension benefits, net of tax	4,956				4,956
Ending balance at Sep. 30, 2021	2,038,468	$ 1,172	1,718,504	414,656	(95,864)
Ending balance (in shares) at Sep. 30, 2021		117,163,000
Common stock issued for employee stock-based awards	0	$ 18	(18)
Common stock issued for employee stock-based awards (in shares)		1,737,000
Shares surrendered by employees to pay taxes related to stock-based awards	(68,991)	$ (6)	(68,985)
Shares surrendered by employees to pay taxes related to stock-based awards (in shares)		(597,000)
Common stock issued for employee stock purchase plan	21,207	$ 2	21,205
Common stock issued for employee stock purchase plan (in shares)		215,000
Compensation expense from stock-based awards	174,863		174,863
Net Income (Loss)	313,081			313,081
Gain (loss) on net investment hedges, net of tax	17,556				17,556
Repurchases of common stock	$ (125,000)	$ (11)	(124,989)
Repurchases of common stock (in shares)	(1,050,000.00)	(1,046,000)
Foreign currency translation adjustment	$ (92,768)				(92,768)
Unrealized loss on marketable securities, net of tax	0
Change in pension benefits, net of tax	17,618				17,618
Ending balance at Sep. 30, 2022	$ 2,296,034	$ 1,175	1,720,580	727,737	(153,458)
Ending balance (in shares) at Sep. 30, 2022	117,472,000	117,472,000
Common stock issued for employee stock-based awards	$ 0	$ 18	(18)
Common stock issued for employee stock-based awards (in shares)		1,798,000
Shares surrendered by employees to pay taxes related to stock-based awards	(82,768)	$ (7)	(82,761)
Shares surrendered by employees to pay taxes related to stock-based awards (in shares)		(620,000)
Common stock issued for employee stock purchase plan	21,652	$ 2	21,650
Common stock issued for employee stock purchase plan (in shares)		196,000
Compensation expense from stock-based awards	161,454		161,454
Net Income (Loss)	245,540			245,540
Gain (loss) on net investment hedges, net of tax	$ (7,516)				(7,516)
Repurchases of common stock (in shares)	0
Foreign currency translation adjustment	$ 45,692				45,692
Unrealized loss on marketable securities, net of tax	0
Change in pension benefits, net of tax	(2,798)				(2,798)
Ending balance at Sep. 30, 2023	$ 2,677,290	$ 1,188	$ 1,820,905	$ 973,277	$ (118,080)
Ending balance (in shares) at Sep. 30, 2023	118,846,000	118,846,000