CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 42,357	$ 33,277
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	15,168	17,047
Share-based compensation	28,300	20,596
Deferred income taxes	(2,056)	2,453
Tax effect from share-based payment arrangements	13,508	9,306
Excess tax benefits from share-based payment arrangements	(14,008)	(8,616)
Provision for doubtful accounts, net	870	0
Net loss on sales of property and equipment	0	12
Changes in operating assets and liabilities:
Accounts receivable	566	(15,072)
Prepaid expenses and other assets	532	(15,777)
Accounts payable	233	10,655
Accrued compensation and employee benefits	(9,836)	(18,912)
Other liabilities	(6,901)	(6,948)
Deferred revenue	9,593	15,261
Net cash provided by operating activities	78,326	43,282
Cash flows from investing activities:
Purchases of property and equipment	(7,807)	(10,251)
Cash paid for acquisitions, net of cash acquired	0	(56,621)
Distribution from cost method investees	0	75
Net cash used in investing activities	(7,807)	(66,797)
Cash flows from financing activities:
Proceeds from revolving line of credit	44,000	152,000
Payments on revolving line of credit	(41,000)	(40,000)
Proceeds from issuance of treasury stock under employee stock plans	6,757	11,853
Taxes paid related to net share settlement of equity awards	(25,881)	(15,992)
Dividends paid	(1,245)	(1,260)
Repurchases of common stock	(68,390)	(100,713)
Excess tax benefits from share-based payment arrangements	14,008	8,616
Net cash provided by (used in) financing activities	(71,751)	14,504
Effect of exchange rate changes on cash	486	(9,223)
Decrease in cash and cash equivalents	(746)	(18,234)
Cash and cash equivalents, beginning of period	86,120	105,075
Cash and cash equivalents, end of period	85,374	86,841
Supplemental disclosures of cash flow information:
Income taxes refunds (payments), net	2,648	(24,496)
Cash paid for interest	13,273	14,709
Supplemental disclosures of non-cash investing and financing activities:
Purchase of property and equipment included in accounts payable	$ 1,028	$ 4,742