Consolidated Statements of Stockholder's Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance at Sep. 30, 2024	$ 3,214,398	$ 1,202	$ 1,965,307	$ 1,349,610	$ (101,721)
Beginning balance (in shares) at Sep. 30, 2024		120,155,000
Common stock issued for employee stock-based awards	0	$ 8	(8)
Common stock issued for employee stock-based awards (in shares)		810,000
Shares surrendered by employees to pay taxes related to stock-based awards	(53,321)	$ (3)	(53,318)
Shares surrendered by employees to pay taxes related to stock-based awards (in shares)		(282,000)
Common stock issued for employee stock purchase plan	13,307	$ 1	13,306
Common stock issued for employee stock purchase plan (in shares)		89,000
Compensation expense from stock-based awards	134,575		134,575
Repurchases of common stock, including excise tax	(150,334)	$ (9)	(150,325)
Repurchases of common stock, including excise tax (in shares)		(846,000)
Net Income (Loss)	244,876			244,876
Gain (loss) on net investment hedges, net of tax	10,226				10,226
Foreign currency translation adjustment	(27,795)				(27,795)
Change in defined benefit pension items, net of tax	531				531
Ending balance at Mar. 31, 2025	3,386,463	$ 1,199	1,909,537	1,594,486	(118,759)
Ending balance (in shares) at Mar. 31, 2025		119,926,000
Beginning balance at Dec. 31, 2024	3,229,821	$ 1,202	1,936,411	1,431,842	(139,634)
Beginning balance (in shares) at Dec. 31, 2024		120,219,000
Common stock issued for employee stock-based awards	0	$ 1	(1)
Common stock issued for employee stock-based awards (in shares)		115,000
Shares surrendered by employees to pay taxes related to stock-based awards	(6,128)	$ 0	(6,128)
Shares surrendered by employees to pay taxes related to stock-based awards (in shares)		(34,000)
Common stock issued for employee stock purchase plan	13,307	$ 1	13,306
Common stock issued for employee stock purchase plan (in shares)		89,000
Compensation expense from stock-based awards	41,278		41,278
Repurchases of common stock, including excise tax	(75,334)	$ (5)	(75,329)
Repurchases of common stock, including excise tax (in shares)		(463,000)
Net Income (Loss)	162,644			162,644
Gain (loss) on net investment hedges, net of tax	(15,014)				(15,014)
Foreign currency translation adjustment	36,202				36,202
Change in defined benefit pension items, net of tax	(313)				(313)
Ending balance at Mar. 31, 2025	3,386,463	$ 1,199	1,909,537	1,594,486	(118,759)
Ending balance (in shares) at Mar. 31, 2025		119,926,000
Beginning balance at Sep. 30, 2025	$ 3,826,229	$ 1,195	1,822,590	2,083,607	(81,163)
Beginning balance (in shares) at Sep. 30, 2025	119,536,000	119,536,000
Common stock issued for employee stock-based awards	$ 0	$ 9	(9)
Common stock issued for employee stock-based awards (in shares)		845,000
Shares surrendered by employees to pay taxes related to stock-based awards	(52,628)	$ (4)	(52,624)
Shares surrendered by employees to pay taxes related to stock-based awards (in shares)		(300,000)
Common stock issued for employee stock purchase plan	13,162	$ 1	13,161
Common stock issued for employee stock purchase plan (in shares)		99,000
Compensation expense from stock-based awards	158,753		158,753
Repurchases of common stock, including excise tax	(831,487)	$ (46)	(831,441)
Repurchases of common stock, including excise tax (in shares)		(4,682,000)
Net Income (Loss)	757,241			757,241
Gain (loss) on net investment hedges, net of tax	6,156				6,156
Foreign currency translation adjustment	(17,885)				(17,885)
Change in defined benefit pension items, net of tax	332				332
Ending balance at Mar. 31, 2026	$ 3,859,873	$ 1,155	1,110,430	2,840,848	(92,560)
Ending balance (in shares) at Mar. 31, 2026	115,498,000	115,498,000
Beginning balance at Dec. 31, 2025	$ 3,842,419	$ 1,189	1,672,252	2,250,125	(81,147)
Beginning balance (in shares) at Dec. 31, 2025		118,892,000
Common stock issued for employee stock-based awards		$ 1	(1)
Common stock issued for employee stock-based awards (in shares)		64,000
Shares surrendered by employees to pay taxes related to stock-based awards	(2,797)	$ (1)	(2,796)
Shares surrendered by employees to pay taxes related to stock-based awards (in shares)		(17,000)
Common stock issued for employee stock purchase plan	13,162	$ 1	13,161
Common stock issued for employee stock purchase plan (in shares)		99,000
Compensation expense from stock-based awards	58,105		58,105
Repurchases of common stock, including excise tax	(630,326)	$ (35)	(630,291)
Repurchases of common stock, including excise tax (in shares)		(3,540,000)
Net Income (Loss)	590,723			590,723
Gain (loss) on net investment hedges, net of tax	6,745				6,745
Foreign currency translation adjustment	(18,414)				(18,414)
Change in defined benefit pension items, net of tax	256				256
Ending balance at Mar. 31, 2026	$ 3,859,873	$ 1,155	$ 1,110,430	$ 2,840,848	$ (92,560)
Ending balance (in shares) at Mar. 31, 2026	115,498,000	115,498,000