Segments - Schedule of Significant Expenses and Net Income for Reportable Segment (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Revenue		$ 2,739,226	$ 2,298,472	$ 2,097,053
Net income		733,997	376,333	245,540
Operating Segments
Segment Reporting Information [Line Items]
Revenue		2,739,226	2,298,472	2,097,053
Cost of revenue, adjusted	[1]	389,465	384,882	384,438
Operating expenses, adjusted	[2]	1,047,636	1,019,250	953,720
Other segment items	[3]	568,128	518,007	513,355
Net income		$ 733,997	$ 376,333	$ 245,540

[1] Cost of revenue, adjusted excludes stock-based compensation and amortization of acquired intangible assets.

[2] Operating expenses, adjusted excludes stock-based compensation, amortization of acquired intangible assets, acquisition and transaction-related charges, and Impairment and other charges (credits), net.

[3] Other segment items include stock-based compensation; amortization of acquired intangible assets; acquisition and transaction-related charges; Impairment and other charges (credits), net; Other income (expense), net; and Provision for income taxes.