CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 84,959	$ 86,492
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	5,227	7,026
Share-based compensation	29,878	25,132
Deferred income taxes	3,905	(298)
Net (gain) loss on marketable securities	592	(1,768)
Non-cash operating lease costs	4,115	4,000
Provision for doubtful accounts, net	325	219
Net loss on sales and abandonment of property and equipment	51	62
Gains on product line asset sales and business divestiture	0	(7,334)
Changes in operating assets and liabilities:
Accounts receivable	58,428	33,130
Prepaid expenses and other assets	157	(7,310)
Accounts payable	(268)	(1,479)
Accrued compensation and employee benefits	(40,335)	(46,704)
Other liabilities	(14,904)	(12,241)
Deferred revenue	(7,249)	(980)
Net cash provided by operating activities	124,881	77,947
Cash flows from investing activities:
Purchases of property and equipment	(895)	(3,045)
Proceeds from sales of marketable securities	129	567
Purchases of marketable securities	(2,763)	(1,741)
Proceeds from product line asset sales and business divestiture	2,257	8,291
Purchase of equity investment	0	(210)
Net cash provided by (used in) investing activities	(1,272)	3,862
Cash flows from financing activities:
Proceeds from revolving line of credit and term loan	620,000	116,000
Payments on revolving line of credit and term loan	(788,000)	(80,000)
Proceeds from issuance of senior notes	550,000	0
Payments on debt issuance costs	(8,200)	0
Payments on finance leases	0	(176)
Proceeds from issuance of treasury stock under employee stock plans	550	57
Taxes paid related to net share settlement of equity awards	(47,024)	(85,678)
Repurchases of common stock	(482,755)	(50,011)
Net cash used in financing activities	(155,429)	(99,808)
Effect of exchange rate changes on cash	(1,377)	5,267
Decrease in cash and cash equivalents	(33,197)	(12,732)
Cash and cash equivalents, beginning of period	195,354	157,394
Cash and cash equivalents, end of period	162,157	144,662
Supplemental disclosures of cash flow information:
Cash paid for income taxes, net of refunds of $72 and $221 during the quarters ended December 31, 2021 and 2020, respectively	1,570	3,186
Cash paid for interest	19,396	17,858
Supplemental disclosures of non-cash investing and financing activities:
Purchase of property and equipment included in accounts payable	67	13
Unsettled repurchases of common stock	$ 18,870	$ 0