Note 7 - Net Income Per Share - Summary of Earnings Per Share, Basic, Two Class Method (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 25, 2017	Feb. 27, 2016	Feb. 25, 2017	Feb. 27, 2016
Net income available to shareholders	$ 22,516	$ 23,498	$ 50,730	$ 59,388
Income allocated to – Basic:
Allocation of net income for Basic	$ 22,516	$ 23,498	$ 50,730	$ 59,388
Weighted average number of shares outstanding – Basic:
Weighted average number of shares for Basic (in shares)	20,290	20,132	20,281	20,120
Common Class A [Member]
Income allocated to – Basic:
Allocation of net income for Basic	$ 17,836	$ 18,691	$ 40,178	$ 47,232
Weighted average number of shares outstanding – Basic:
Weighted average number of shares for Basic (in shares)	15,305	15,241	15,295	15,230
Income per share – Basic:
Earnings per share for Basic (in dollars per share)	$ 1.17	$ 1.23	$ 2.63	$ 3.10
Common Class B [Member]
Income allocated to – Basic:
Allocation of net income for Basic	$ 4,518	$ 4,704	$ 10,184	$ 11,896
Weighted average number of shares outstanding – Basic:
Weighted average number of shares for Basic (in shares)	4,846	4,795	4,846	4,795
Income per share – Basic:
Earnings per share for Basic (in dollars per share)	$ 0.93	$ 0.98	$ 2.10	$ 2.48
Unvested Participating Shares [Member]
Income allocated to – Basic:
Allocation of net income for Basic	$ 162	$ 103	$ 368	$ 260
Weighted average number of shares outstanding – Basic:
Weighted average number of shares for Basic (in shares)	139	96	140	95