CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	$ 137,540	$ 93,769
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	23,734	22,329
Share-based compensation	61,931	54,631
Deferred income taxes	247	(3,643)
Net (gain) loss on marketable securities	635	(635)
Provision for doubtful accounts, net	509	541
Net loss on sales of property and equipment	22	28
Changes in operating assets and liabilities:
Accounts receivable	(53,288)	2,922
Prepaid expenses and other assets	(5,369)	(3,587)
Accounts payable	631	2,623
Accrued compensation and employee benefits	4,217	(1,977)
Other liabilities	(6,164)	(21)
Deferred revenue	291	(3,891)
Net cash provided by operating activities	164,936	163,089
Cash flows from investing activities:
Purchases of property and equipment	(18,170)	(24,220)
Proceeds from sales of marketable securities	3,228	3,005
Purchases of marketable securities	(5,858)	(5,509)
Net cash used in investing activities	(20,800)	(26,724)
Cash flows from financing activities:
Proceeds from revolving line of credit	167,000	371,000
Payments on revolving line of credit	(109,000)	(480,000)
Proceeds from issuance of senior notes	0	400,000
Payments on senior notes	0	(131,000)
Payments on debt issuance costs	0	(7,869)
Proceeds from issuance of treasury stock under employee stock plans	16,073	2,492
Taxes paid related to net share settlement of equity awards	(51,208)	(42,872)
Repurchases of common stock	(178,926)	(229,540)
Net cash used in financing activities	(156,061)	(117,789)
Effect of exchange rate changes on cash	710	(4,265)
Increase (decrease) in cash and cash equivalents	(11,215)	14,311
Cash and cash equivalents, beginning of period	90,023	105,618
Cash and cash equivalents, end of period	78,808	119,929
Supplemental disclosures of cash flow information:
Cash paid for income taxes, net of refunds	12,058	9,975
Cash paid for interest	33,401	20,501
Supplemental disclosures of non-cash investing and financing activities:
Purchase of property and equipment included in accounts payable	690	5,282
Unsettled repurchases of common stock	0	7,601
Capital lease obligations incurred	$ 6,416	$ 0