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Note 7 - Stock-based Compensation (Details Textual) - USD ($)		3 Months Ended		6 Months Ended
	Feb. 28, 2020	Mar. 28, 2020	Mar. 30, 2019	Mar. 28, 2020	Mar. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)		$ 7.39	$ 7.96	$ 7.39	$ 7.96
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)				3 years
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)				10 years
Share-based Payment Arrangement, Expense		$ 403,000	$ 383,000	$ 463,000	$ 438,000
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount		319,000		$ 319,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)				1 year 240 days
Restricted Stock Units (RSUs) [Member]
Share-based Payment Arrangement, Expense		$ 538,000	462,000	$ 664,000	$ 581,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)					1 year 222 days
Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount			$ 671,000		$ 671,000
Restricted Stock Units (RSUs) [Member] \| Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)				1 year
Restricted Stock Units (RSUs) [Member] \| Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)				3 years
The 2015 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized (in shares)	750,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)		790,000		790,000