Note 6 - Weighted-average Assumptions to Value Share-based Awards Granted (Details) - $ / shares	12 Months Ended
	Dec. 26, 2015	Dec. 27, 2014	Dec. 28, 2013
Employee Stock Purchase Plan [Member]
Dividend yield	2.20%	2.40%	2.60%
Expected volatility	35.30%	35.30%	38.40%
Risk-free interest rate	0.10%	0.10%	0.10%
Expected term (years)	182 days	182 days	182 days
Weighted-average grant date fair value per share (in dollars per share)	$ 2.71	$ 2.52	$ 2.32
Employee Stock Option [Member]
Dividend yield	2.10%	2.00%	2.60%
Expected volatility	39.10%	42.50%	44.90%
Risk-free interest rate	1.60%	1.90%	1.10%
Expected term (years)	5 years 328 days	5 years 328 days	6 years 146 days
Weighted-average grant date fair value per share (in dollars per share)	$ 3.46	$ 4.39	$ 3.37
Restricted Stock Units (RSUs) [Member]
Dividend yield	2.10%	2.20%	2.50%
Performance Stock Units [Member]
Dividend yield	2.10%	2.20%	2.50%