Note 6 - Employee Benefit Plans - Performance Based Stock Unit Activity Under Share-based Compensation Plans (Details) - Equity Based Performance Stock Units [Member] - $ / shares shares in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Outstanding, beginning of year, units (in shares)	364	340	334
Outstanding, beginning of year, wt. avg. (in dollars per share)	$ 18.72	$ 17.89	$ 14.31
Granted, units (in shares)	200	167	89
Granted, wt. avg. (in dollars per share)	$ 13.18	$ 14.11	$ 24.32
Released, units (in shares)	(39)	(36)	(41)
Released, wt. avg. (in dollars per share)	$ 21.40	$ 11.35	$ 9.92
Cancelled, units (in shares)	(100)	(107)	(42)
Cancelled, wt. avg. (in dollars per share)	$ 20.25	$ 11.35	$ 10.69
Outstanding, end of year, units (in shares)	425	364	340
Outstanding, end of year, wt. avg. (in dollars per share)	$ 15.51	$ 18.72	$ 17.89