Note 6 - Employee Stock 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. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Outstanding, beginning of year, units (in shares)	403	376	334
Outstanding, beginning of year, wt. avg. (in dollars per share)	$ 11.04	$ 10.80	$ 10.49
Granted, units (in shares)	185	222	156
Granted, wt. avg. (in dollars per share)	$ 17.60	$ 11.38	$ 10.69
Released, units (in shares)	(186)	(172)	(38)
Released, wt. avg. (in dollars per share)	$ 11.35	$ 11.27	$ 9.52
Cancelled, units (in shares)	(68)	(23)	(76)
Cancelled, wt. avg. (in dollars per share)	$ 11.94	$ 8.75	$ 9.86
Outstanding, end of year, units (in shares)	334	403	376
Outstanding, end of year, wt. avg. (in dollars per share)	$ 14.31	$ 11.04	$ 10.80