CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income	$ 109,448	$ 86,502	$ 94,879
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	31,633	33,889	32,632
Share-based compensation	55,509	45,308	36,362
Deferred income taxes	(26,007)	(5,934)	(16,026)
Tax effect from share-based payment arrangements	24,184	12,530	6,035
Excess tax benefits from share-based payment arrangements	(25,037)	(13,795)	(6,808)
Provision of doubtful accounts	2,011	0	1,485
Net (gain) loss on sales of property and equipment	6	2,210	(10)
Changes in operating assets and liabilities:
Accounts receivable	(18,225)	(4,602)	(13,649)
Prepaid expenses and other assets	12,848	(15,462)	(1,754)
Accounts payable	564	(3,672)	3,174
Accrued compensation and employee benefits	17,079	(1,506)	17,450
Other liabilities	(4,282)	4,113	15,566
Deferred revenue	5,500	(6,604)	5,698
Net cash provided by operating activities	185,231	132,977	175,034
Cash flows from investing activities:
Purchases of property and equipment	(21,969)	(24,999)	(12,590)
Cash paid for acquisitions, net of cash acquired	(5,683)	(56,992)	(7,253)
Distribution from cost method investees	37	75	0
Net cash used in investing activities	(27,615)	(81,916)	(19,843)
Cash flows from financing activities:
Proceeds from revolving line of credit	122,000	249,000	145,000
Payments on revolving line of credit and other short-term loans	(99,000)	(116,000)	(61,000)
Payments on senior notes	(60,000)	(71,000)	(8,000)
Proceeds from issuance of treasury stock under employee stock plans	17,828	18,258	18,851
Taxes paid related to net share settlement of equity awards	(29,955)	(19,461)	(12,297)
Dividends paid	(2,489)	(2,508)	(2,714)
Repurchases of common stock	(138,399)	(130,719)	(217,039)
Excess tax benefits from share-based payment arrangements	25,037	13,795	6,808
Net cash used in financing activities	(164,978)	(58,635)	(130,391)
Effect of exchange rate changes on cash	(2,832)	(11,381)	(2,903)
Increase (decrease) in cash and cash equivalents	(10,194)	(18,955)	21,897
Cash and cash equivalents, beginning of year	86,120	105,075	83,178
Cash and cash equivalents, end of year	75,926	86,120	105,075
Supplemental disclosures of cash flow information:
Cash paid for income taxes, net of refunds of $11,363, $1,592 and $3,424 during the years ended September 30, 2016, 2015 and 2014, respectively	10,855	33,752	22,367
Cash paid for interest	26,884	30,470	28,209
Supplemental disclosures of non-cash investing and financing activities:
Purchase of property and equipment included in accounts payable	$ 3,287	$ 436	$ 363