CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 192,124	$ 126,482	$ 133,414
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	31,612	30,182	36,214
Share-based compensation	82,973	74,814	61,222
Deferred income taxes	7,701	10,584	(6,248)
Provision of doubtful accounts	518	623	1,640
Net gain (loss) on marketable securities	761	(1,449)	0
Gain on sale of cost-method investment	0	(10,000)	0
Net loss on sales of property and equipment	127	231	14
Changes in operating assets and liabilities:
Accounts receivable	(36,176)	(8,266)	2,858
Prepaid expenses and other assets	(55,507)	(9,790)	(9,863)
Accounts payable	1,885	843	(2,027)
Accrued compensation and employee benefits	22,380	7,352	6,464
Other liabilities	1,463	6,246	(81)
Deferred revenue	10,489	(4,800)	2,037
Net cash provided by operating activities	260,350	223,052	225,644
Cash flows from investing activities:
Purchases of property and equipment	(23,981)	(31,299)	(19,828)
Proceeds from sales of marketable securities	3,480	3,230	0
Purchases of marketable securities	(6,404)	(6,050)	0
Proceeds from Sale and Maturity of Other Investments	0	20,000	0
Payments to Acquire Other Investments	0	0	(777)
Cash paid for acquisitions, net of cash acquired	(15,855)	0	0
Net cash used in investing activities	(42,760)	(14,119)	(20,605)
Cash flows from financing activities:
Proceeds from revolving line of credit	229,000	427,000	190,000
Payments on revolving line of credit	(141,000)	(531,000)	(84,000)
Proceeds from issuance of senior notes	0	400,000	0
Payments on senior notes	(28,000)	(131,000)	(72,000)
Payments on debt issuance costs	0	(7,849)	0
Repayments of Long-term Capital Lease Obligations	(945)	0	0
Proceeds from issuance of treasury stock under employee stock plans	22,788	11,023	14,474
Taxes paid related to net share settlement of equity awards	(52,996)	(44,205)	(40,232)
Dividends paid	0	0	(1,238)
Repurchases of common stock	(228,894)	(342,596)	(187,629)
Net cash used in financing activities	(200,047)	(218,627)	(180,625)
Effect of exchange rate changes on cash	(1,140)	(5,901)	5,278
Increase (decrease) in cash and cash equivalents	16,403	(15,595)	29,692
Cash and cash equivalents, beginning of year	90,023	105,618	75,926
Cash and cash equivalents, end of year	106,426	90,023	105,618
Supplemental disclosures of cash flow information:
Cash paid for income taxes, net of refunds of $1,372, $3,079 and $3,757 during the years ended September 30, 2019, 2018 and 2017, respectively	18,779	13,398	31,315
Cash paid for interest	39,924	26,106	26,083
Supplemental disclosures of non-cash investing and financing activities:
Capital Lease Obligation Incurred	5,803	0	0
Unsettled repurchases of common stock	0	0	5,661
Purchase of property and equipment included in accounts payable	$ 1,448	$ 1,913	$ 1,751