CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 54,921	$ 40,007
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,856	7,967
Share-based compensation	23,145	21,854
Deferred income taxes	(1,016)	(50)
Net (gain) loss on marketable securities	(944)	3,050
Amortization of Leased Asset	4,493	0
Provision for doubtful accounts, net	281	180
Net (gain) loss on sales of property and equipment	48	(22)
Changes in operating assets and liabilities:
Accounts receivable	22,391	18,191
Prepaid expenses and other assets	(21,711)	(10,787)
Accounts payable	10,349	1,671
Accrued compensation and employee benefits	(35,566)	(28,918)
Other liabilities	(4,379)	(4,848)
Deferred revenue	497	562
Net Cash Provided by (Used in) Operating Activities	60,365	48,857
Cash flows from investing activities:
Purchases of property and equipment	(6,500)	(6,474)
Proceeds from sales of marketable securities	167	102
Purchases of marketable securities	(2,733)	(2,303)
Distribution from other investments	55	0
Net Cash Provided by (Used in) Investing Activities	(9,011)	(8,675)
Cash flows from financing activities:
Proceeds from revolving line of credit	117,000	103,000
Payments on revolving line of credit	(367,000)	(35,000)
Proceeds from issuance of senior notes	350,000	0
Payments on debt issuance costs	(6,805)	0
Payment from finance lease	(425)	0
Proceeds from issuance of treasury stock under employee stock plans	5,091	7,550
Taxes paid related to net share settlement of equity awards	(86,047)	(42,987)
Repurchases of common stock	(60,009)	(82,700)
Net Cash Provided by (Used in) Financing Activities	(48,195)	(50,137)
Effect of exchange rate changes on cash	1,631	(172)
Increase (decrease) in cash and cash equivalents	4,790	(10,127)
Cash and cash equivalents, beginning of period	106,426	90,023
Cash and cash equivalents, end of period	111,216	79,896
Supplemental disclosures of cash flow information:
Cash paid for income taxes, net of refunds	2,391	1,394
Interest Paid, Excluding Capitalized Interest, Operating Activities	12,856	13,439
Supplemental disclosures of non-cash investing and financing activities:
Purchase of property and equipment included in accounts payable	93	433
Finance lease obligations incurred	$ 3,045	$ 0