Note 13 - Common Stock and Earnings Per Share - Shares of Common Stock Outstanding (Details) - shares		8 Months Ended	12 Months Ended
		Aug. 31, 2017	Aug. 31, 2018	Aug. 31, 2017	Aug. 31, 2016
Balance, beginning of year (September 1) (in shares)			39,023,032	40,038,000	41,317,000
Common stock issued for employee stock plans (in shares)			711,000	693,000	823,000
Repurchase of common stock (in shares)		(1,554,822)	(1,534,398)
Balance (in shares)		39,023,032	38,192,586	39,023,032	40,038,000
Repurchase of Common Stock from Employees [Member]
Repurchase of common stock (in shares)	[1]		(8,000)	(50,000)	(28,000)
Share Repurchase Program [Member]
Repurchase of common stock (in shares)			(1,534,000)	(1,555,000)	(1,478,000)
ASR Agreement [Member]
Repurchase of common stock (in shares)				(103,000)	(596,000)

[1] For fiscal 2018, 2017 and 2016, the Company repurchased 8,070, 49,771 and 27,625 shares, or $1.5 million, $7.8 million and $4.5 million, of common stock, respectively, in settlement of employee tax withholding obligations due upon the vesting of restricted stock.