Note 6 - Employee Benefit Plans - Post-retirement Benefit Obligation to Funded Status and Liability (Details) - Postretirement Health Coverage [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019
Accumulated benefit obligation at beginning of year	$ (2,571)	$ (2,880)
Interest cost	(75)	(115)
Actuarial gain	134	258
Benefits paid	114	166
Accumulated benefit obligation at end of year	(2,398)	(2,571)
Plan assets at end of year	0	0
Funded status	$ (2,398)	$ (2,571)