CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 37,901	$ 19,241
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	9,058	7,441
Share-based compensation	14,519	14,700
Deferred income taxes	0	5,986
Tax effect from share-based payment arrangements	0	9,615
Provision for doubtful accounts, net	463	438
Changes in operating assets and liabilities:
Accounts receivable	8,253	18,005
Prepaid expenses and other assets	(16,876)	(14,807)
Accounts payable	(725)	2,022
Accrued compensation and employee benefits	(29,030)	(16,381)
Other liabilities	(2,091)	(2,438)
Deferred revenue	11,506	6,807
Net cash provided by operating activities	32,978	50,629
Cash flows from investing activities:
Purchases of property and equipment	(4,319)	(4,294)
Net cash used in investing activities	(4,319)	(4,294)
Cash flows from financing activities:
Proceeds from revolving line of credit	60,000	26,000
Payments on revolving line of credit	(10,000)	(15,000)
Proceeds from issuance of treasury stock under employee stock plans	3,663	1,199
Taxes paid related to net share settlement of equity awards	(35,598)	(24,462)
Dividends paid	(618)	(622)
Repurchases of common stock	(30,442)	(28,382)
Net cash used in financing activities	(12,995)	(41,267)
Effect of exchange rate changes on cash	(3,489)	(478)
Increase in cash and cash equivalents	12,175	4,590
Cash and cash equivalents, beginning of period	75,926	86,120
Cash and cash equivalents, end of period	88,101	90,710
Supplemental disclosures of cash flow information:
Cash paid for income taxes, net of refunds	7,463	4,364
Cash paid for interest	5,851	5,823
Supplemental disclosures of non-cash investing and financing activities:
Purchase of property and equipment included in accounts payable	$ 3,816	$ 267