Stockholders' Equity (Details)	1 Months Ended									3 Months Ended			12 Months Ended
	Feb. 28, 2017 shares	Aug. 31, 2016 installment $ / shares shares	Feb. 29, 2016 shares	Aug. 31, 2015 installment $ / shares shares	Feb. 28, 2015 shares	Aug. 31, 2014 item $ / shares shares	Feb. 28, 2014 shares	Sep. 30, 2013 item $ / shares shares	Oct. 31, 2012 shares	Nov. 30, 2016 $ / shares shares	Nov. 30, 2015 $ / shares shares	May 31, 2015 shares	Aug. 31, 2017 $ / shares shares	Aug. 31, 2016 $ / shares shares	Aug. 31, 2015 $ / shares shares	Aug. 31, 2014 $ / shares shares	Aug. 31, 2013 shares	Mar. 31, 2012 $ / shares	Nov. 30, 2005 shares	Oct. 31, 2002 shares
Non-executive members of management | August 31, 2021 vesting date
Stock Based Compensation
Shares granted										8,805
Number of Shares
Granted (in shares)										8,805
Non-employee members of BOD
Stock Based Compensation
Shares granted													2,407	4,554	5,361
Number of Shares
Unvested restricted stock, beginning balance (in shares)										4,554	5,361		4,554	5,361	4,878
Granted (in shares)													2,407	4,554	5,361
Vested (in shares)													(4,554)	(5,361)	(4,878)
Unvested restricted stock, ending balance (in shares)		4,554		5,361		4,878							2,407	4,554	5,361	4,878
Weighted Average Grant Date Fair Value
Unvested restricted stock, beginning balance (in dollars per share) | $ / shares										$ 48.12	$ 36.19		$ 48.12	$ 36.19	$ 29.52
Granted (in dollars per share) | $ / shares													91.05	48.12	36.19
Vested (in dollars per share) | $ / shares													48.12	36.19	29.52
Unvested restricted stock, ending balance (in dollars per share) | $ / shares		$ 48.12		$ 36.19		$ 29.52							$ 91.05	$ 48.12	$ 36.19	$ 29.52
Officers and employees
Stock Based Compensation
Shares granted													42,160	25,330	36,610
Shares forfeited															12,186
Exercise price (in dollar per share) | $ / shares		$ 20.57		$ 16.92		$ 15.43							$ 34.21	$ 20.57	$ 16.92	$ 15.43
Number of Shares
Unvested restricted stock, beginning balance (in shares)										55,328	48,269		55,328	48,269	56,079
Granted (in shares)													42,160	25,330	36,610
Vested (in shares)													(23,516)	(18,271)	(32,234)
Forfeited or cancelled (in shares)															(12,186)
Unvested restricted stock, ending balance (in shares)		55,328		48,269		56,079							73,972	55,328	48,269	56,079
Weighted Average Grant Date Fair Value
Unvested restricted stock, beginning balance (in dollars per share) | $ / shares										$ 39.20	$ 35.68		$ 39.20	$ 35.68	$ 18.83
Granted (in dollars per share) | $ / shares													60.67	39.07	37.76
Vested (in dollars per share) | $ / shares													38.81	29.72	16.68
Forfeited or cancelled (in dollars per share) | $ / shares															14.63
Unvested restricted stock, ending balance (in dollars per share) | $ / shares		$ 39.20		$ 35.68		$ 18.83							$ 51.56	$ 39.20	$ 35.68	$ 18.83
Stock options
Stock Based Compensation
Common stock available for future issuance (in shares)													1,078,015
Stock options | Non-executive members of management
Stock Based Compensation
Exercise price (in dollar per share) | $ / shares																		$ 14.62
Stock options | Executive officers | August 31, 2019 vesting date
Stock Based Compensation
Shares authorized		23,563												23,563
Exercise price (in dollar per share) | $ / shares		$ 64.37												$ 64.37
Restricted stock | Non-employee members of BOD
Stock Based Compensation
Vesting period	12 months		12 months		12 months		12 months
Shares granted	2,407		4,554		5,361		4,878
Number of Shares
Granted (in shares)	2,407		4,554		5,361		4,878
Time-based restricted stock | Executive officers
Stock Based Compensation
Number of equal annual installments | installment		5
Vesting period		5 years
Shares granted		16,312
Number of Shares
Granted (in shares)		16,312
Time-based restricted stock | Executive officers | August 31, 2019 vesting date
Stock Based Compensation
Shares granted		7,768
Number of Shares
Granted (in shares)		7,768
Time-based restricted stock | Executive officers | August 31, 2021 vesting date
Stock Based Compensation
Shares granted		8,544
Number of Shares
Granted (in shares)		8,544
2013 Plan
Stock Based Compensation
Shares authorized									1,200,000
Common stock available for future issuance (in shares)													1,078,015
2005 Incentive Plan
Stock Based Compensation
Shares authorized																			1,000,000
2001 Senior Management Stock Plan
Stock Based Compensation
Shares authorized																				1,500,000
2001 Non-Employee Director Stock Option Plan
Stock Based Compensation
Shares authorized																				180,000
2013 LTIP | Performance and service based restricted stock | Executive officers and other members of management
Stock Based Compensation
Shares granted									11,861								11,861
Cumulative shares granted																	23,722
Number of Shares
Granted (in shares)									11,861								11,861
2013 LTIP | Time-based restricted stock | Executive officers and other members of management | August 31, 2013 vesting date
Stock Based Compensation
Shares forfeited									1,931
Number of Shares
Forfeited or cancelled (in shares)									(1,931)
2013 LTIP | Time-based restricted stock | Executive officers and other members of management | August 31, 2015 vesting date
Stock Based Compensation
Shares forfeited									16,505
Number of Shares
Forfeited or cancelled (in shares)									(16,505)
2014 LTIP | Stock options | Executive officers and other members of management
Stock Based Compensation
Shares granted								25,969
Number of equal annual allotments in which awards will vest | item								3
Exercise price (in dollar per share) | $ / shares								$ 29.72
Number of Shares
Granted (in shares)								25,969
2014 LTIP | Performance and service based restricted stock | Executive officers and other members of management
Stock Based Compensation
Shares granted								7,529								5,485
Cumulative shares granted																13,014
Number of Shares
Granted (in shares)								7,529								5,485
2014 LTIP | Time-based restricted stock | Executive officers and other members of management | August 31, 2016 vesting date
Stock Based Compensation
Shares forfeited								8,323
Number of Shares
Forfeited or cancelled (in shares)								(8,323)
2014 LTIP | Time-based restricted stock | Executive officers and other members of management | August 31, 2014 vesting date
Stock Based Compensation
Shares forfeited								1,040
Number of Shares
Forfeited or cancelled (in shares)								(1,040)
2015 LTIP | Executive officers and other members of management
Stock Based Compensation
Adjusted shares															5,685
Cumulative shares granted															12,678
2015 LTIP | Stock options | Executive officers and other members of management
Stock Based Compensation
Cumulative shares granted						22,750
Number of equal annual allotments in which awards will vest | item						3
Exercise price (in dollar per share) | $ / shares						$ 35.50										$ 35.50
2015 LTIP | Stock options | Executive officers and other members of management | August 31, 2024 vesting date
Stock Based Compensation
Shares forfeited						7,438
Number of Shares
Forfeited or cancelled (in shares)						(7,438)
2015 LTIP | Stock options | Executive officers and other members of management | September 1, 2024 vesting date
Stock Based Compensation
Shares forfeited						15,312
Number of Shares
Forfeited or cancelled (in shares)						(15,312)
2015 LTIP | Performance and service based restricted stock | Executive officers and other members of management | August 31, 2017 vesting date
Stock Based Compensation
Shares granted						6,993
Number of Shares
Granted (in shares)						6,993
2015 LTIP | Time-based restricted stock | Non-executive members of management
Stock Based Compensation
Shares granted												16,000
Number of Shares
Granted (in shares)												16,000
2015 LTIP | Time-based restricted stock | Non-executive members of management | April 16, 2020 vesting date
Stock Based Compensation
Shares granted												15,000
Number of Shares
Granted (in shares)												15,000
2015 LTIP | Time-based restricted stock | Non-executive members of management | January 31, 2018 vesting date
Stock Based Compensation
Shares granted												1,000
Number of Shares
Granted (in shares)												1,000
2015 LTIP | Time-based restricted stock | Executive officers and other members of management
Stock Based Compensation
Shares granted						8,132
Number of Shares
Granted (in shares)						8,132
2015 LTIP | Time-based restricted stock | Executive officers and other members of management | August 31, 2017 vesting date
Stock Based Compensation
Shares granted						7,005
Number of Shares
Granted (in shares)						7,005
2015 LTIP | Time-based restricted stock | Executive officers and other members of management | September 1, 2024 vesting date
Stock Based Compensation
Shares granted						1,127
Number of Shares
Granted (in shares)						1,127
2016 LTIP | Executive officers and other members of management
Stock Based Compensation
Adjusted shares														6,277
Cumulative shares granted														13,239
2016 LTIP | Stock options | Executive officers and other members of management | August 31, 2018 vesting date
Stock Based Compensation
Shares granted				21,275
Number of equal annual allotments in which awards will vest | installment				3
Exercise price (in dollar per share) | $ / shares				$ 39.50											$ 39.50
Number of Shares
Granted (in shares)				21,275
2016 LTIP | Restricted stock | Non-executive members of management | October 20, 2020 Vesting date
Stock Based Compensation
Shares granted											5,000
Number of Shares
Granted (in shares)											5,000
2016 LTIP | Performance and service based restricted stock | Executive officers and other members of management | August 31, 2018 vesting date
Stock Based Compensation
Shares granted				6,962
Number of Shares
Granted (in shares)				6,962
2016 LTIP | Time-based restricted stock | Executive officers and other members of management | August 31, 2018 vesting date
Stock Based Compensation
Shares granted				7,683
Number of Shares
Granted (in shares)				7,683
2017 LTIP | Stock options | Executive officers and other members of management
Stock Based Compensation
Shares authorized		15,028												15,028
Stock options expiring on August 31, 2026 (in shares)		5,596
Stock options expiring on September 1, 2026 (in shares)		9,432
Number of equal annual allotments in which awards will vest | installment		3
Exercise price (in dollar per share) | $ / shares		$ 64.37												$ 64.37
2017 LTIP | Performance and service based restricted stock | Executive officers and other members of management | August 31, 2019 vesting date
Stock Based Compensation
Shares granted		5,399
Number of Shares
Granted (in shares)		5,399
2017 LTIP | Time-based restricted stock | Executive officers and other members of management | August 31, 2019 vesting date
Stock Based Compensation
Shares granted		5,367
Number of Shares
Granted (in shares)		5,367