CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Tax Benefit From Stock Based Compensation [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total
Balance at Aug. 31, 2015	$ 3	$ 403,168	$ 10,711	$ (101,512)	$ 283,611	$ (29,397)	$ 566,584
Balance (in shares) at Aug. 31, 2015	30,978,000					793,000
Purchase of treasury stock						$ (2,017)	(2,017)
Purchase of treasury stock (in shares)						27,000
Issuance of restricted stock award
Issuance of restricted stock award (in shares)	233,000
Exercise of stock options		80					80
Exercise of stock options (in shares)	4,000
Stock-based compensation		6,731	579				7,310
Dividend paid to stockholders					(10,629)		(10,629)
Dividends payable to stockholders					(10,629)		(10,629)
Net income					66,451		66,451
Other comprehensive income (loss)				(4,919)			(4,919)
Balance at May. 31, 2016	$ 3	409,979	11,290	(106,431)	328,804	$ (31,414)	612,231
Balance (in shares) at May. 31, 2016	31,215,000					820,000
Balance at Aug. 31, 2016	$ 3	412,369	11,321	(103,951)	351,060	$ (32,731)	$ 638,071
Balance (in shares) at Aug. 31, 2016	31,238,000					836,000	30,401,307
Purchase of treasury stock						$ (2,011)	$ (2,011)
Purchase of treasury stock (in shares)						25,000
Issuance of restricted stock award
Issuance of restricted stock award (in shares)	48,000
Forfeiture of restricted stock awards
Forfeiture of restricted stock awards (in shares)	(35,000)
Exercise of stock options		433					433
Exercise of stock options (in shares)	8,000
Stock-based compensation		7,328	231				7,559
Dividend paid to stockholders					(10,641)		(10,641)
Dividends payable to stockholders					(10,643)		(10,643)
Net income					70,926		70,926
Other comprehensive income (loss)				(4,307)			(4,307)
Balance at May. 31, 2017	$ 3	$ 420,130	$ 11,552	$ (108,258)	$ 400,702	$ (34,742)	$ 689,387
Balance (in shares) at May. 31, 2017	31,259,000					861,000	30,398,239