CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Cash flows from operating activities:
Net income	$ 422,831	$ 315,143
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,905	6,950
Share-based compensation	89,579	82,358
Deferred income taxes	14,728	(12,781)
Net loss on marketable securities	4,980	3,174
Non-cash operating lease costs	4,711	5,213
Provision for (benefit from) doubtful accounts	(6)	990
Net (gain) loss on sales and abandonment of property and equipment	(5)	70
Changes in operating assets and liabilities:
Accounts receivable	(82,251)	(66,718)
Prepaid expenses and other assets	(21,383)	(43,213)
Accounts payable	4,075	1,796
Accrued compensation and employee benefits	(27,940)	(28,183)
Other liabilities	(16,093)	(14,016)
Deferred revenue	(3,691)	18,132
Net cash provided by operating activities	397,440	268,915
Cash flows from investing activities:
Purchases of property and equipment	(492)	(2,960)
Capitalized internal-use software costs	(17,256)	(13,638)
Proceeds from sales of marketable securities	6,109	1,495
Purchases of marketable securities	(9,509)	(4,780)
Net cash used in investing activities	(21,148)	(19,883)
Cash flows from financing activities:
Proceeds from revolving line of credit and term loans	880,000	450,000
Payments on revolving line of credit and term loans	(890,000)	(132,500)
Proceeds from issuance of senior notes	1,000,000	0
Payments on senior notes	(400,000)	0
Payments on debt issuance costs	(9,013)	0
Payments on finance leases	(2,834)	(3,016)
Proceeds from issuance of treasury stock under employee stock plans	14,935	16,062
Taxes paid related to net share settlement of equity awards	(105,767)	(198,531)
Repurchases of common stock, inclusive of excise tax	(776,565)	(379,738)
Net cash used in financing activities	(289,244)	(247,723)
Effect of exchange rate changes on cash	(1,765)	(5,335)
Increase (decrease) in cash and cash equivalents	85,283	(4,026)
Cash and cash equivalents, beginning of period	134,136	150,667
Cash and cash equivalents, end of period	219,419	146,641
Supplemental disclosures of cash flow information:
Cash paid for income taxes, net of refunds of $7,796 and $663 during the six-month periods ended March 31, 2026 and 2025, respectively	120,142	92,213
Cash paid for interest	93,172	60,939
Supplemental disclosures of non-cash investing and financing activities:
Purchase of property and equipment included in accounts payable	67	14
Unsettled repurchases of common stock, inclusive of excise tax accrued, but not yet paid	$ 15,800	$ 412