Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Cash flows from operating activities:
Net income (loss)	$ 21,799	$ (10,245)
Adjustments to reconcile net income (loss) to net cash provided (used) by operating activities:
Depreciation and amortization	42,727	42,683
Stock-based compensation	35,357	39,565
Non-cash portion of restructuring charges	0	260
Other non-cash items, net	189	479
Loss on disposal of fixed assets	22	0
Changes in operating assets and liabilities, excluding the effects of acquisitions:
Accounts receivable	32,027	15,373
Accounts payable and accrued expenses	(9,474)	11,183
Accrued compensation and benefits	(29,656)	(51,769)
Deferred revenue	59,027	27,457
Accrued income taxes	(14,134)	(14,680)
Other current assets and prepaid expenses	(7,540)	(11,424)
Other noncurrent assets and liabilities	5,931	(20,332)
Net cash provided by operating activities	136,275	28,550
Cash flows from investing activities:
Additions to property and equipment	(11,139)	(14,789)
Purchase of intangible asset	(3,000)	0
Purchases of short- and long-term marketable securities	(13,794)	(3,420)
Proceeds from maturities of short- and long-term marketable securities	8,240	4,700
Acquisitions of businesses, net of cash acquired	(3,000)	0
Proceeds from sales of investments	0	15,218
Net cash provided (used) by investing activities	(22,693)	1,709
Cash flows from financing activities:
Borrowings under credit facility	50,000	100,000
Repayments of borrowings under credit facility	(120,000)	(140,000)
Proceeds from issuance of common stock	7,472	3,978
Credit facility origination costs	0	(184)
Contingent consideration	(3,176)	(2,711)
Payments of withholding taxes in connection with vesting of stock-based awards	(33,942)	(19,166)
Net cash used in financing activities	(99,646)	(58,083)
Effect of exchange rate changes on cash and cash equivalents	5,837	(6,795)
Net increase (decrease) in cash and cash equivalents	19,773	(34,619)
Cash and cash equivalents, beginning of period	280,003	277,935
Cash and cash equivalents, end of period	$ 299,776	$ 243,316