Note 6 - Employee Stock Benefit Plans - Post-retirement Benefit Obligation to Funded Status and Liability (Details) - Postretirement Health Coverage [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Accumulated benefit obligation at beginning of year	$ 2,490	$ 2,649
Interest cost	95	109
Actuarial (gain) loss	677	(185)
Benefits paid	(114)	(83)
Accumulated benefit obligation at end of year	3,148	2,490
Plan assets at end of year
Funded status	$ (3,148)	$ (2,490)