CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income	$ 113,209	$ 73,388
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	15,535	15,786
Share-based compensation	45,933	42,336
Deferred income taxes	(1,213)	74
Net loss on marketable securities	2,526	1,300
Amortization of Leased Asset	10,000	0
Provision for doubtful accounts, net	2,459	391
Net (gain) loss on sales of property and equipment	59	(5)
Changes in operating assets and liabilities:
Accounts receivable	(13,823)	(5,015)
Prepaid expenses and other assets	(19,656)	(12,219)
Accounts payable	1,833	(2,210)
Accrued compensation and employee benefits	(37,339)	(16,970)
Other liabilities	(4,659)	(2,672)
Deferred revenue	6,995	2,462
Net Cash Provided by (Used in) Operating Activities	121,859	96,646
Cash flows from investing activities:
Purchases of property and equipment	(13,166)	(10,644)
Proceeds from sales of marketable securities	3,385	2,267
Purchases of marketable securities	(5,232)	(4,396)
Distribution from other investments	55	0
Net Cash Provided by (Used in) Investing Activities	(14,958)	(12,773)
Cash flows from financing activities:
Proceeds from revolving line of credit	156,000	138,000
Payments on revolving line of credit	(377,000)	(80,000)
Proceeds from issuance of senior notes	350,000	0
Payments on debt issuance costs	(6,840)	0
Payment from finance lease	(712)	0
Proceeds from issuance of treasury stock under employee stock plans	23,216	12,850
Taxes paid related to net share settlement of equity awards	(97,000)	(48,470)
Repurchases of common stock	(148,008)	(119,723)
Net Cash Provided by (Used in) Financing Activities	(100,344)	(97,343)
Effect of exchange rate changes on cash	(4,017)	332
Increase (decrease) in cash and cash equivalents	2,540	(13,138)
Cash and cash equivalents, beginning of period	106,426	90,023
Cash and cash equivalents, end of period	108,966	76,885
Supplemental disclosures of cash flow information:
Cash paid for income taxes, net of refunds	4,475	7,962
Interest Paid, Excluding Capitalized Interest, Operating Activities	16,181	19,686
Supplemental disclosures of non-cash investing and financing activities:
Purchase of property and equipment included in accounts payable	1,920	77
Repurchases of Common Stock Incurred Not Yet Paid	8,002	0
Finance lease obligations incurred	$ 5,148	$ 0