Note 8 - Stockholders' Equity (Details Textual) - $ / shares							6 Months Ended
	Jan. 23, 2019	Oct. 24, 2018	Sep. 01, 2018	Jan. 24, 2018	Nov. 20, 2017	Sep. 01, 2017	Feb. 28, 2019	Feb. 28, 2018	Jan. 18, 2019	Jan. 17, 2019	Nov. 16, 2018	Aug. 31, 2018
Common Stock, Shares Authorized							15,000,000		15,000,000	10,000,000		15,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross							70,884	47,252
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period							0	1,500
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price								$ 10.25
Stock Issued During Period, Shares, Employee Stock Purchase Plans			874			891
Stock Repurchased and Retired During Period, Shares							0	0
Dividends Payable, Date to be Paid	Feb. 22, 2019	Nov. 21, 2018		Feb. 21, 2018	Dec. 21, 2017
Dividends Payable, Date of Record	Feb. 06, 2019	Nov. 07, 2018		Feb. 08, 2018	Dec. 08, 2017
The 2019 Plan [member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized							400,000				400,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross							0
The 2007 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross							70,884	47,252
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price							$ 36.45	$ 18.35