CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities:
Net income	$ 50,009	$ 23,754
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	10,049	12,770
Share-based compensation	9,384	8,205
Deferred income taxes	(1,967)	818
Tax effect from share-based payment arrangements	3,160	(144)
Excess tax benefits from share-based payment arrangements	(3,414)	(1,127)
Net amortization of premium on marketable securities	178	365
Benefit from provision for doubtful accounts, net		(582)
Net loss on sales of property and equipment	2	155
Changes in operating assets and liabilities:
Accounts receivable	(1,680)	7,275
Prepaid expenses and other assets	1,077	3,911
Accounts payable	4,629	6,257
Accrued compensation and employee benefits	(2,209)	(9,788)
Other liabilities	(2,853)	1,580
Deferred revenue	17,111	6,169
Net cash provided by operating activities	83,476	59,618
Cash flows from investing activities:
Purchases of property and equipment	(13,364)	(5,106)
Purchases of marketable securities	(43,071)
Proceeds from sales of marketable securities		13,644
Proceeds from maturities of marketable securities	103,659	54,545
Distribution from cost method investees	(199)	75
Net cash provided by investing activities	47,025	63,158
Cash flows from financing activities:
Proceeds from issuances of common stock under employee stock option and purchase plans	33,401	6,889
Dividends paid	(1,426)	(1,599)
Repurchases of common stock	(156,773)	(19,311)
Excess tax benefits from share-based payment arrangements	3,414	1,127
Net cash used in financing activities	(121,384)	(12,894)
Effect of exchange rate changes on cash	1,167	2,213
Increase in cash and cash equivalents	10,284	112,095
Cash and cash equivalents, beginning of year	135,752	146,199
Cash and cash equivalents, end of year	146,036	258,294
Supplemental disclosures of cash flow information:
Cash paid for income taxes, net of refunds	18,027	8,696
Cash paid for interest	$ 15,712	$ 16,082