Note 11 - Common Stock and Earnings Per Share - Shares of Common Stock Outstanding (Details) - shares		3 Months Ended		6 Months Ended
		Feb. 28, 2019	Feb. 28, 2018	Feb. 28, 2019	Feb. 28, 2018
Balance (in shares)				38,192,586	39,023,000
Common stock issued for employee stock plans (in shares)				426,000	495,000
Repurchase of common stock (in shares)		(214,945)	(420,000)	(489,945)	(584,920)
Balance (in shares)		38,100,165	38,927,000	38,100,165	38,927,000
Repurchase of Common Stock from Employees [Member]
Repurchase of common stock (in shares)	[1]			(28,000)	(6,000)
Share Repurchase Program [Member]
Repurchase of common stock (in shares)				(490,000)	(585,000)

[1] For the six months ended February 28, 2019 and 2018, the Company repurchased 27,852 and 5,563 shares, or $6.1 million and $1.0 million, of common stock, respectively, in settlement of employee tax withholding obligations due upon the vesting of restricted stock.