Consolidated Statements of Shareholders' Equity Statement - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	AOCI Attributable to Parent	Retained Earnings
Beginning Balance (in shares) at Sep. 30, 2022		59,860
Beginning Balance at Sep. 30, 2022	$ 2,468,978	$ 91,048	$ (26,176)	$ 2,404,106
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of employee stock options (in shares)		14
Exercise of employee stock options	435	$ 435
Issuance of stock under employee stock purchase plan (in shares)		179
Issuance of stock under employee stock purchase plan	21,745	$ 21,745
Issuance of restricted stock (in shares)		376
Issuance of restricted stock	0
Stock Repurchased and Retired During Period, Shares		(263)
Stock Repurchased and Retired During Period, Value	(40,005)	$ (40,005)
Cost of Issuance of Treasury Stock, Shares		(49)
Taxes paid related to net share settlement of equity awards	(7,037)	$ (7,037)
Stock-based compensation	62,874	$ 62,874
Net income	72,402			72,402
Other Comprehensive Income (Loss)	2,957		2,957
Ending Balance ( in shares) at Dec. 31, 2022		60,117
Ending Balance at Dec. 31, 2022	$ 2,582,349	$ 129,060	(23,219)	2,476,508
Beginning Balance (in shares) at Sep. 30, 2023	59,207	59,207
Beginning Balance at Sep. 30, 2023	$ 2,800,232	$ 24,399	(23,221)	2,799,054
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of employee stock options (in shares)		14
Exercise of employee stock options	408	$ 408
Issuance of stock under employee stock purchase plan (in shares)		188
Issuance of stock under employee stock purchase plan	21,468	$ 21,468
Issuance of restricted stock (in shares)		355
Issuance of restricted stock	0
Stock Repurchased and Retired During Period, Shares		(922)
Repurchase of common stock, including excise taxes		$ (77,099)		(74,139)
Stock Repurchased and Retired During Period, Including Excise Tax	(151,238)
Stock Repurchased and Retired During Period, Value	(150,018)
Cost of Issuance of Treasury Stock, Shares		(45)
Taxes paid related to net share settlement of equity awards	(6,830)	$ (6,830)
Stock-based compensation	56,002	$ 56,002
Net income	138,382			138,382
Other Comprehensive Income (Loss)	$ 2,553		2,553
Ending Balance ( in shares) at Dec. 31, 2023	58,797	58,797
Ending Balance at Dec. 31, 2023	$ 2,860,977	$ 18,348	$ (20,668)	$ 2,863,297