Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Basic Earnings per Share
Net Income	$ 11,413	$ 11,855	$ 8,383	$ 10,363	$ 10,855	$ 7,531	$ 6,972	$ 7,449	$ 42,014	$ 32,807	$ 26,318
Less: Allocated to participating securities									454	266	214
Net income available to common shareholders									$ 41,560	$ 32,541	$ 26,104
Basic weighted average shares outstanding									9,249,343	9,167,333	9,086,043
Net income per share - Basic (in dollars per share)	$ 1.22	$ 1.27	$ 0.90	$ 1.11	$ 1.17	$ 0.81	$ 0.75	$ 0.81	$ 4.49	$ 3.55	$ 2.87
Diluted Earnings per Share
Net Income	$ 11,413	$ 11,855	$ 8,383	$ 10,363	$ 10,855	$ 7,531	$ 6,972	$ 7,449	$ 42,014	$ 32,807	$ 26,318
Basic weighted average shares outstanding									9,249,343	9,167,333	9,086,043
Additional dilutive common stock equivalents (in shares)									108,071	126,744	168,011
Diluted weighted average shares outstanding									9,357,414	9,294,077	9,254,054
Net income per share - Diluted (in dollars per share)	$ 1.21	$ 1.26	$ 0.89	$ 1.10	$ 1.16	$ 0.80	$ 0.74	$ 0.80	$ 4.44	$ 3.50	$ 2.82
Net income available to common shareholders, per common and common equivalent share
Basic (in dollars per share)	1.22	1.27	0.90	1.11	1.17	0.81	0.75	0.81	4.49	3.55	2.87
Diluted (in dollars per share)	$ 1.21	$ 1.26	$ 0.89	$ 1.10	$ 1.16	$ 0.80	$ 0.74	$ 0.80	$ 4.44	$ 3.50	$ 2.82
Antidilutive securities
Antidilutive stock options excluded from computation of earnings per share amount (in shares)									0	9,354	20,271