CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities:
Net income	$ 199,193	$ 189,342
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	8,294	10,656
Share-based compensation	56,755	57,814
Deferred income taxes	(18,360)	3,004
Net (gain) loss on marketable securities	(1,681)	3,209
Non-cash operating lease costs	7,613	8,166
Provision for doubtful accounts	738	650
Gain (Loss) on Disposition of Assets	1,941	0
Net loss on sales and abandonment of property and equipment	24	166
Changes in operating assets and liabilities:
Accounts receivable	(13,789)	33,098
Prepaid expenses and other assets	(17,078)	5,179
Accounts payable	(2,810)	(4,105)
Accrued compensation and employee benefits	(32,318)	(41,745)
Other liabilities	(2,425)	(14,159)
Deferred revenue	29	(3,791)
Net cash provided by operating activities	182,244	247,484
Cash flows from investing activities:
Purchases of property and equipment	(2,377)	(3,293)
Proceeds from sales of marketable securities	4,631	3,354
Purchases of marketable securities	(8,015)	(5,982)
Proceeds from product line asset sales, net of cash transferred	(6,126)	2,257
Net cash used in investing activities	(11,887)	(3,664)
Cash flows from financing activities:
Proceeds from revolving line of credit and term loan	228,000	800,000
Payments on revolving line of credit and term loan	(158,500)	(806,750)
Proceeds from issuance of senior notes	0	550,000
Payments on debt issuance costs	0	(8,819)
Proceeds from issuance of treasury stock under employee stock plans	15,217	11,117
Taxes paid related to net share settlement of equity awards	(73,672)	(47,849)
Repurchases of common stock	(184,290)	(760,861)
Net cash used in financing activities	(173,245)	(263,162)
Effect of exchange rate changes on cash	7,457	(1,793)
Increase (decrease) in cash and cash equivalents	4,569	(21,135)
Cash and cash equivalents, beginning of period	133,202	195,354
Cash and cash equivalents, end of period	137,771	174,219
Supplemental disclosures of cash flow information:
Cash paid for income taxes, net of refunds of $548 and $1,003 during the six-month periods ended March 31, 2023 and 2022, respectively	72,800	30,788
Cash paid for interest	46,801	21,368
Supplemental disclosures of non-cash investing and financing activities:
Purchase of property and equipment included in accounts payable	9	139
Unsettled repurchases of common stock	$ 6,981	$ 4,735