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Stockholders' Equity (Weighted Average Assumptions Used to Estimate Fair Value of Stock Option Grants) (Details) - Incentive and Non-Statutory Stock Options [Member] - USD ($)
12 Months Ended
Sep. 24, 2019
Sep. 25, 2018
[1]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected term (years) 7 years 6 months 7 years 6 months
Expected volatility, minimum 70.65% 75.09%
Expected volatility, maximum 70.80% 80.70%
Risk free interest rate, minimum 3.01% 1.49%
Risk free interest rate, maximum 3.10% 2.80%
Expected dividends $ 0 $ 0
[1] Excluding options issued in the exchange program