Stockholders' Equity - Additional Disclosures (Details) $ / shares in Units, $ in Thousands	1 Months Ended						12 Months Ended
	Feb. 28, 2017	Feb. 29, 2016	Feb. 28, 2015	Feb. 28, 2014	Oct. 31, 2012 item $ / shares shares	Mar. 31, 2012 item $ / shares shares	Aug. 31, 2017 USD ($) $ / shares shares	Aug. 31, 2016 USD ($) $ / shares shares	Aug. 31, 2015 USD ($) $ / shares shares	Aug. 31, 2014 shares
Additional disclosures
Tax (expense) / benefit realized from stock options exercised, vesting of restricted stock and issuance of stock pursuant to grants of restricted stock units (in dollars) | $								$ 1,784	$ 1,088
Unrecognized expense related to all stock-based compensation (in dollars) | $							$ 3,176
Non-employee members of BOD
Additional disclosures
Outstanding at the end of the period (in shares)							2,407	4,554	5,361	4,878
Officers and employees
Options Exercisable
Number Exercisable (in shares)							115,187
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 25.58
Options outstanding
Options outstanding at the beginning of the period (in shares)							194,551	313,389	463,901
Granted (in shares)							38,591	21,275	22,750
Exercised (in shares)							(80,168)	(140,113)	(169,038)
Forfeited or cancelled (in shares)									(4,224)
Options outstanding at the end of the period (in shares)							152,974	194,551	313,389
Weighted Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share) | $ / shares							$ 20.57	$ 16.92	$ 15.43
Granted (in dollars per share) | $ / shares							64.37	39.50	35.50
Exercised (in dollars per share) | $ / shares							15.62	15.27	15.21
Forfeited or cancelled (in dollars per share) | $ / shares									22.25
Options outstanding at the end of the period (in dollars per share) | $ / shares							$ 34.21	$ 20.57	$ 16.92
Additional disclosures
Outstanding at the end of the period (in shares)							73,972	55,328	48,269	56,079
Stock options
Options Outstanding
Number Outstanding (in shares)							152,974
Weighted Avg. Remaining Contractual Life							6 years 4 months 24 days
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 34.21
Aggregate Intrinsic Value (in dollars) | $							$ 9,069
Options Exercisable
Number Exercisable (in shares)							115,187
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 25.58
Aggregate Intrinsic Value (in dollars) | $							$ 7,823
Additional disclosures
Weighted average grant date fair value of options granted (in dollars per share) | $ / shares							$ 21.22	$ 13.80	$ 12.10
Total pretax intrinsic value of stock options exercised (in dollars) | $							$ 6,243	$ 6,880	$ 3,972
Common stock available for future issuance (in shares)							1,078,015
Tax (expense) / benefit realized from stock options exercised, vesting of restricted stock and issuance of stock pursuant to grants of restricted stock units (in dollars) | $							$ 1,917	$ 1,784	$ 1,088
Unrecognized expense related to all stock-based compensation (in dollars) | $							$ 2,713
Stock options | $12.70
Options Outstanding
Number Outstanding (in shares)							15,105
Weighted Avg. Remaining Contractual Life							3 years
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 12.70
Aggregate Intrinsic Value (in dollars) | $							$ 1,220
Options Exercisable
Number Exercisable (in shares)							15,105
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 12.70
Aggregate Intrinsic Value (in dollars) | $							$ 1,220
Stock options | $12.77
Options Outstanding
Number Outstanding (in shares)							16,953
Weighted Avg. Remaining Contractual Life							4 years
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 12.77
Aggregate Intrinsic Value (in dollars) | $							$ 1,369
Options Exercisable
Number Exercisable (in shares)							16,953
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 12.77
Aggregate Intrinsic Value (in dollars) | $							$ 1,369
Stock options | $16.00
Options Outstanding
Number Outstanding (in shares)							25,087
Weighted Avg. Remaining Contractual Life							5 years 1 month 6 days
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 16.00
Aggregate Intrinsic Value (in dollars) | $							$ 1,944
Options Exercisable
Number Exercisable (in shares)							25,087
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 16.00
Aggregate Intrinsic Value (in dollars) | $							$ 1,944
Stock options | $16.53
Options Outstanding
Number Outstanding (in shares)							3,926
Weighted Avg. Remaining Contractual Life							3 years 8 months 12 days
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 16.53
Aggregate Intrinsic Value (in dollars) | $							$ 302
Options Exercisable
Number Exercisable (in shares)							3,926
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 16.53
Aggregate Intrinsic Value (in dollars) | $							$ 302
Stock options | $29.72
Options Outstanding
Number Outstanding (in shares)							16,246
Weighted Avg. Remaining Contractual Life							6 years
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 29.72
Aggregate Intrinsic Value (in dollars) | $							$ 1,036
Options Exercisable
Number Exercisable (in shares)							16,246
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 29.72
Aggregate Intrinsic Value (in dollars) | $							$ 1,036
Stock options | $35.50
Options Outstanding
Number Outstanding (in shares)							17,965
Weighted Avg. Remaining Contractual Life							7 years
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 35.50
Aggregate Intrinsic Value (in dollars) | $							$ 1,042
Options Exercisable
Number Exercisable (in shares)							17,965
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 35.50
Aggregate Intrinsic Value (in dollars) | $							$ 1,042
Stock options | $39.50
Options Outstanding
Number Outstanding (in shares)							19,101
Weighted Avg. Remaining Contractual Life							8 years
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 39.50
Aggregate Intrinsic Value (in dollars) | $							$ 1,032
Options Exercisable
Number Exercisable (in shares)							13,264
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 39.50
Aggregate Intrinsic Value (in dollars) | $							$ 716
Stock options | 64.37
Options Outstanding
Number Outstanding (in shares)							38,591
Weighted Avg. Remaining Contractual Life							9 years
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 64.37
Aggregate Intrinsic Value (in dollars) | $							$ 1,124
Options Exercisable
Number Exercisable (in shares)							6,641
Weighted Average Exercise Price (in dollars per share) | $ / shares							$ 64.37
Aggregate Intrinsic Value (in dollars) | $							$ 194
Stock options | Non-executive members of management
Stockholders' Equity
Number of equal annual allotments in which options will vest beginning from the end of the fiscal year | item						3
Options outstanding
Granted (in shares)						6,630
Weighted Average Exercise Price
Options outstanding at the end of the period (in dollars per share) | $ / shares						$ 14.62
Stock options | Executive officers and other members of management | 2013 LTIP
Stockholders' Equity
Number of equal annual allotments in which options will vest beginning from the end of the fiscal year | item					3
Options outstanding
Granted (in shares)					43,964
Weighted Average Exercise Price
Options outstanding at the end of the period (in dollars per share) | $ / shares					$ 16.00
Restricted stock
Additional disclosures
Unrecognized expense related to all stock-based compensation (in dollars) | $							$ 463
Restricted stock | Non-employee members of BOD
Stockholders' Equity
Vesting period	12 months	12 months	12 months	12 months