Income Taxes - Summary of Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Income Tax Disclosure [Abstract]
Income before income taxes	$ 746,799	$ 205,249	$ 949,774	$ 298,403
Provision for income taxes	$ 156,076	$ 42,605	$ 192,533	$ 53,527
Effective income tax rate	21.00%	21.00%	20.00%	18.00%