Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities
Net income	$ 187,356	$ 165,131
Adjustments to reconcile net income to net cash provided by operating activities:
Realized (gain) loss on disposition of assets and investments	(7)	31
Stock-based compensation	90,506	80,006
Provisions for doubtful accounts and sales returns	455	522
Depreciation and amortization	30,278	27,847
Deferred income taxes	(214)	7,424
Changes in operating assets and liabilities:
Accounts receivable	(26,152)	12,726
Inventories	1,504	(1,462)
Other current assets	1,449	(16,302)
Other assets	(942)	(126)
Accounts payable and accrued liabilities	21,072	1,844
Deferred revenue	59,347	59,348
Net cash provided by operating activities	364,652	336,989
Investing activities
Purchases of investments	(146,236)	(138,925)
Maturities of investments	187,660	173,165
Sales of investments	40,737	47,742
(Increase) decrease in restricted cash	(36)	8
Acquisition of intangible assets	(4,000)	(3,250)
Purchases of property and equipment	(23,715)	(29,793)
Net cash provided by investing activities	54,410	48,947
Financing activities
Excess tax benefit from stock-based compensation	5,239	1,378
Proceeds from the exercise of stock options and purchases of stock under employee stock purchase plan	18,868	18,594
Repurchase of common stock	(300,042)	(400,077)
Net cash used in financing activities	(275,935)	(380,105)
Net increase in cash and cash equivalents	143,127	5,831
Effect of exchange rate changes on cash and cash equivalents	(1,925)	2,034
Cash and cash equivalents, beginning of period	514,571	390,460
Cash and cash equivalents, end of period	$ 655,773	$ 398,325