Note 7 - Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
	Mar. 28, 2020	Sep. 28, 2019
Options outstanding, balance (in shares)	388
Weighted average exercise price per share (in dollars per share)	$ 26.16
Options outstanding, granted (in shares)	67
Weighted average exercise price per share (in dollars per share)	$ 22.09
Options outstanding, exercised (in shares)
Weighted average exercise price per share, exercised (in dollars per share)
Options outstanding, balance (in shares)	455	388
Weighted average exercise price per share (in dollars per share)	$ 25.57	$ 26.16
Contractual term - weighted average, balance (Year)	7 years 251 days
Aggregate intrinsic value, balance	$ 25
Options outstanding, vested and anticipated to vest in future (in shares)	451
Weighted average exercise price per share, vested and anticipated to vest in future (in dollars per share)	$ 25.58
Contractual term - weighted average, vested and anticipated to vest in future (Year)	7 years 248 days
Aggregate intrinsic value, vested and anticipated to vest in future	$ 25
Options outstanding, exercisable (in shares)	227
Weighted average exercise price per share, exercisable (in dollars per share)	$ 27.67
Contractual term - weighted average, exercisable (Year)	6 years 98 days
Aggregate intrinsic value, exercisable	$ 25
Minimum [Member]
Exercise price per share, balance, lower (in dollars per share)	$ 10.23	10.23
Exercise price per share, granted, lower (in dollars per share)	22.09
Exercise price per share, exercised, lower (in dollars per share)
Maximum [Member]
Exercise price per share, balance, upper (in dollars per share)	41.85	$ 41.85
Exercise price per share, granted, upper (in dollars per share)	22.09
Exercise price per share, exercised, upper (in dollars per share)