Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 02, 2016	Apr. 04, 2015	Apr. 02, 2016	Apr. 04, 2015	Sep. 30, 2015
Income Tax Disclosure [Line Items]
Effective income tax rate	(45.00%)	(1293.00%)	(26.00%)	(3.00%)
Income before income taxes	$ (3,569)	$ 387	$ (23,115)	$ 34,794
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	(4,000)	(4,000)	(7,000)	(8,000)
Deferred Other Tax Expense (Benefit)		(1,400)		(1,400)
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount			(2,600)	(2,100)
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions		$ (3,100)		$ (3,100)
Unrecognized tax benefits	14,900		14,900		$ 14,100
Income tax provision upon recognition of unrecognized tax benefit	13,300		13,300
Unrecognized tax benefits that would impact valuation allowance	4,700		4,700
Potentail reduction in unrecognized tax benefits and accrued interest over next 12 months	$ (4,000)		$ (4,000)