Equity Incentive Plans - Additional Information (Details) $ / shares in Units, $ in Thousands		12 Months Ended
		Sep. 30, 2024 USD ($) shares $ / shares	Sep. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2022 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Issuable per Restricted Stock Unit | shares		1
Stock-based compensation		$ 223,461	$ 206,459	$ 174,863
Total unrecognized compensation cost		$ 190,300
Weighted average remaining recognition period, in months		17 months
Common stock were available for grant under the 2000 plan | shares		6,100,000
Common stock were reserved for issuance | shares		2,100,000
ESPP maximum contribution percentage		10.00%
ESPP maximum contribution amount by employee		$ 25,000
ESPP purchase price as a % of stock price		85.00%
Vesting term for outstanding awards		1 year
Shares withheld for tax withholding obligation | shares		600,000	600,000	600,000
Payments of withholding taxes in connection with vesting of stock-based awards		$ 102,001	$ 82,448	$ 68,991
Liability classified awards related to stock-based compensation		47,700	44,900
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation		$ 6,800	$ 6,800	$ 6,400
Restricted Shares and Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value per share | $ / shares		$ 164.73	$ 130.64	$ 114.31
TSR Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value per share | $ / shares		209.16
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value per share | $ / shares	[1]	$ 164.73
Payments of withholding taxes in connection with vesting of stock-based awards		$ 101,900	$ 82,800	$ 69,000

[1] RSUs granted include 11 shares from prior period rTSR awards that were earned upon achievement of the performance criteria and vested in November 2023 and 42 shares from prior period performance-based awards that were earned upon achievement of the performance criteria and vested in November 2023.