Segments - Schedule of significant expenses and net income for reportable segment (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Revenue		$ 774,303	$ 636,366	$ 1,460,128	$ 1,201,494
Net income		590,723	162,644	757,241	244,876
Operating Segments
Segment Reporting Information [Line Items]
Revenue		774,303	636,366	1,460,128	1,201,494
Cost of revenue, adjusted	[1]	98,711	92,624	202,563	190,208
Operating expenses, adjusted	[2]	264,939	244,432	537,279	520,646
Other segment items	[3]	(180,070)	136,666	(36,955)	245,764
Net income		$ 590,723	$ 162,644	$ 757,241	$ 244,876

[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, net.

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