CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Cash flows from operating activities:
Net income	$ 512,811	$ 429,375	$ 373,541
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	13,827	14,638	20,465
Share-based compensation	149,439	123,847	115,355
Deferred income taxes	(27,330)	(47,378)	7,816
Non-cash operating lease costs	12,423	14,708	15,922
Provision of doubtful accounts	1,675	1,475	2,800
Net (gain) loss on marketable securities	(9,834)	(2,908)	9,269
Net loss on sales and abandonment of property and equipment	438	547	193
Gain on product line asset sale	0	(1,941)	0
Changes in operating assets and liabilities:
Accounts receivable	(34,144)	(70,117)	(31,557)
Prepaid expenses and other assets	(14,034)	(11,904)	7,368
Accounts payable	3,316	2,236	(2,802)
Accrued compensation and employee benefits	3,195	4,631	(3,637)
Other liabilities	7,216	(7,057)	(28,830)
Deferred revenue	13,966	18,763	23,547
Net cash provided by operating activities	632,964	468,915	509,450
Cash flows from investing activities:
Purchases of property and equipment	(8,884)	(4,237)	(6,029)
Capitalized internal-use software costs	(16,667)	0	0
Proceeds from sales of marketable securities	15,930	5,032	8,063
Purchases of marketable securities	(18,372)	(10,623)	(9,963)
Cash transferred, net of proceeds, from product line asset sale and business divestiture	0	(6,126)	2,258
Net cash used in investing activities	(27,993)	(15,954)	(5,671)
Cash flows from financing activities:
Proceeds from revolving line of credit and term loans	947,000	407,000	1,039,000
Payments on revolving line of credit and term loans	(602,000)	(402,000)	(988,250)
Proceeds from issuance of senior notes	0	0	550,000
Payments on debt issuance costs	(706)	0	(8,819)
Payments on finance leases	(1,333)	0	0
Proceeds from issuance of treasury stock under employee stock plans	25,006	22,198	16,026
Taxes paid related to net share settlement of equity awards	(139,188)	(76,673)	(50,942)
Repurchases of common stock	(821,702)	(405,526)	(1,104,180)
Net cash used in financing activities	(592,923)	(455,001)	(547,165)
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1,841	5,616	(18,766)
Increase (decrease) in cash and cash equivalents	13,889	3,576	(62,152)
Cash and cash equivalents, beginning of year	136,778	133,202	195,354
Cash and cash equivalents, end of year	150,667	136,778	133,202
Supplemental disclosures of cash flow information:
Cash paid for income taxes, refunds	859	640	1,090
Income Taxes Paid, Net	133,716	152,775	65,332
Cash paid for interest	106,388	96,877	57,208
Supplemental disclosures of non-cash investing and financing activities:
Unsettled repurchases of common stock	13,391	1,821	0
Purchase of property and equipment included in accounts payable	62	106	22
Finance lease obligation incurred	$ 11,740	$ 0	$ 0