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. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Outstanding, beginning of year, units (in shares)	376	334	238
Outstanding, beginning of year, wt. avg. (in dollars per share)	$ 10.80	$ 10.49	$ 9.32
Granted, units (in shares)	222	156	208
Granted, wt. avg. (in dollars per share)	$ 11.38	$ 10.69	$ 11.34
Released, units (in shares)	(172)	(38)	(38)
Released, wt. avg. (in dollars per share)	$ 11.27	$ 9.52	$ 9.52
Cancelled, units (in shares)	(23)	(76)	(74)
Cancelled, wt. avg. (in dollars per share)	$ 8.75	$ 9.86	$ 9.59
Outstanding, end of year, units (in shares)	403	376	334
Outstanding, end of year, wt. avg. (in dollars per share)	$ 11.04	$ 10.80	$ 10.49