Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2016	Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016	Sep. 30, 2016
Income Tax Disclosure [Line Items]
Effective income tax rate		236.00%	537.00%	(63.00%)	(9.00%)
Income before income taxes		$ 699	$ (704)	$ (6,860)	$ (23,819)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent				35.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount		(9,000)	$ (9,000)	$ (21,000)	(16,000)
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions				1,800
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount					$ 2,600
Unrecognized tax benefits		15,300		15,300		$ 15,500
Income tax provision upon recognition of unrecognized tax benefit		13,400		13,400
Unrecognized tax benefits that would impact valuation allowance		5,100		5,100
Potentail reduction in unrecognized tax benefits and accrued interest over next 12 months		$ (6,000)		$ (6,000)
Korea
Income Tax Disclosure [Line Items]
Income tax examination, estimate of possible loss	$ 12,000