CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income	$ 62,985	$ 42,357
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	18,236	15,168
Share-based compensation	29,231	28,300
Deferred income taxes	0	(2,056)
Tax effect from share-based payment arrangements	0	13,508
Provision for doubtful accounts, net	925	870
Net loss on sales of property and equipment	10	0
Changes in operating assets and liabilities:
Accounts receivable	23,710	566
Prepaid expenses and other assets	(27,415)	532
Accounts payable	(3,534)	233
Accrued compensation and employee benefits	(22,671)	(9,836)
Other liabilities	(3,487)	(6,901)
Deferred revenue	21,407	9,593
Net cash provided by operating activities	99,397	92,334
Cash flows from investing activities:
Purchases of property and equipment	(9,604)	(7,807)
Net cash used in investing activities	(9,604)	(7,807)
Cash flows from financing activities:
Proceeds from revolving line of credit	79,000	44,000
Payments on revolving line of credit	(24,000)	(41,000)
Proceeds from issuance of treasury stock under employee stock plans	9,114	6,757
Taxes paid related to net share settlement of equity awards	(36,914)	(25,881)
Dividends paid	(1,238)	(1,245)
Repurchases of common stock	(74,647)	(68,390)
Net cash used in financing activities	(48,685)	(85,759)
Effect of exchange rate changes on cash	(1,186)	486
Increase (decrease) in cash and cash equivalents	39,922	(746)
Cash and cash equivalents, beginning of period	75,926	86,120
Cash and cash equivalents, end of period	115,848	85,374
Supplemental disclosures of cash flow information:
Cash paid for income taxes, net of refunds	21,557	2,648
Cash paid for interest	12,377	13,273
Supplemental disclosures of non-cash investing and financing activities:
Purchase of property and equipment included in accounts payable	$ 2,757	$ 1,028