Stockholders' Equity (Details)					1 Months Ended										3 Months Ended						12 Months Ended
	Sep. 01, 2018 installment $ / shares shares	Sep. 01, 2017 $ / shares shares	Sep. 01, 2016 installment $ / shares shares	Sep. 01, 2015 shares	Aug. 31, 2019 $ / shares shares	Feb. 28, 2019 shares	Sep. 30, 2018 $ / shares shares	Feb. 28, 2018 shares	Aug. 31, 2017 installment $ / shares shares	Feb. 28, 2017 shares	Aug. 31, 2016 installment $ / shares shares	Feb. 29, 2016 shares	Aug. 31, 2015 installment $ / shares shares	Aug. 31, 2014 item $ / shares shares	Aug. 31, 2019 installment $ / shares shares	Aug. 31, 2018 $ / shares shares	May 31, 2018 installment $ / shares shares	Nov. 30, 2016 $ / shares shares	Nov. 30, 2015 shares	May 31, 2015 shares	Aug. 31, 2019 $ / shares shares	Aug. 31, 2018 $ / shares shares	Aug. 31, 2017 $ / shares shares	Aug. 31, 2016 $ / shares shares	Aug. 31, 2015 $ / shares shares	Oct. 31, 2012 shares	Nov. 30, 2005 shares
Non-employee members of BOD
Stock-Based Compensation
Shares granted																					4,599	2,779	2,407
Number of Shares
Unvested restricted stock, beginning balance (in shares)	2,779	2,407	4,554				2,779											4,554			2,779	2,407	4,554
Granted (in shares)																					4,599	2,779	2,407
Vested (in shares)																					(2,779)	(2,407)	(4,554)
Unvested restricted stock, ending balance (in shares)					4,599				2,407		4,554				4,599	2,779					4,599	2,779	2,407	4,554
Weighted Average Grant Date Fair Value
Unvested restricted stock, beginning balance (in dollars per share) | $ / shares	$ 101.05	$ 91.05	$ 48.12				$ 101.05											$ 48.12			$ 101.05	$ 91.05	$ 48.12
Granted (in dollars per share) | $ / shares																					101.92	101.05	91.05
Vested (in dollars per share) | $ / shares																					101.05	91.05	48.12
Unvested restricted stock, ending balance (in dollars per share) | $ / shares					$ 101.92				$ 91.05		$ 48.12				$ 101.92	$ 101.05					$ 101.92	$ 101.05	$ 91.05	$ 48.12
Officers and employees
Stock-Based Compensation
Shares granted																					7,524	13,922	42,160
Shares forfeited																					3,305
Exercise price (in dollar per share) | $ / shares					$ 57.18				$ 34.21		$ 20.57				$ 57.18	$ 57.18					$ 57.18	$ 57.18	$ 34.21	$ 20.57
Number of Shares
Unvested restricted stock, beginning balance (in shares)	65,579	73,972	55,328				65,579											55,328			65,579	73,972	55,328
Granted (in shares)																					7,524	13,922	42,160
Vested (in shares)																					(25,443)	(22,315)	(23,516)
Forfeited or cancelled (in shares)																					(3,305)
Unvested restricted stock, ending balance (in shares)					44,355				73,972		55,328				44,355	65,579					44,355	65,579	73,972	55,328
Weighted Average Grant Date Fair Value
Unvested restricted stock, beginning balance (in dollars per share) | $ / shares	$ 61.85	$ 51.56	$ 39.20				$ 61.85											$ 39.20			$ 61.85	$ 51.56	$ 39.20
Granted (in dollars per share) | $ / shares																					121.64	83.65	60.67
Vested (in dollars per share) | $ / shares																					65.79	41.35	38.81
Forfeited or cancelled (in dollars per share) | $ / shares																					79.39
Unvested restricted stock, ending balance (in dollars per share) | $ / shares					$ 67.18				$ 51.56		$ 39.20				$ 67.18	$ 61.85					$ 67.18	$ 61.85	$ 51.56	$ 39.20
Stock options
Stock-Based Compensation
Common stock available for future issuance (in shares)																1,057,892						1,057,892
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
Stock-Based Compensation
Shares forfeited							2,472
Number of Shares
Forfeited or cancelled (in shares)							(2,472)
Restricted stock | Non-employee members of BOD
Stock-Based Compensation
Vesting period						12 months		12 months		12 months		12 months
Shares granted						4,599		2,779		2,407		4,554
Number of Shares
Granted (in shares)						4,599		2,779		2,407		4,554
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)					1,057,892										1,057,892						1,057,892
2005 Incentive Plan
Stock-Based Compensation
Shares authorized																											1,000,000
Common stock available for future issuance (in shares)					42,005										42,005						42,005
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
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 | Executive officers and other members of management
Stock-Based Compensation
Adjusted shares																							5,399
2017 LTIP | Non-employee members of BOD
Stock-Based Compensation
Cumulative shares granted																							10,798
2017 LTIP | Stock options | Executive officers and other members of management
Stock-Based Compensation
Shares authorized											15,028													15,028
Stock options expiring earlier (in shares)											5,596
Stock options expiring later (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 | Restricted stock | 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
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
2018 LTIP | Executive officers and other members of management
Stock-Based Compensation
Shares granted																					572
Cumulative shares granted																					4,821
Number of Shares
Granted (in shares)																					572
2018 LTIP | Stock options | Non-executive members of management
Stock-Based Compensation
Shares authorized																	606
Number of equal annual allotments in which awards will vest | installment																	3
Exercise price (in dollar per share) | $ / shares																	$ 104.00
2018 LTIP | Stock options | Executive officers and other members of management
Stock-Based Compensation
Shares authorized									9,622														9,622
Number of equal annual installments | installment									3
Stock options expiring earlier (in shares)									4,591
Stock options expiring later (in shares)									5,031
Exercise price (in dollar per share) | $ / shares									$ 93.50														$ 93.50
2018 LTIP | Restricted stock | Non-executive members of management | 31 August, 2020 vesting date
Stock-Based Compensation
Shares granted																	192
Number of Shares
Granted (in shares)																	192
2018 LTIP | Restricted stock | Executive officers | August 20, 2019 vesting date
Stock-Based Compensation
Shares granted																609
Number of Shares
Granted (in shares)																609
2018 LTIP | Performance and service based restricted stock | Executive officers and other members of management | 31 August, 2020 vesting date
Stock-Based Compensation
Shares granted		4,249
Number of Shares
Granted (in shares)		4,249
2018 LTIP | Time-based restricted stock | Executive officers and other members of management | 31 August, 2020 vesting date
Stock-Based Compensation
Shares granted		3,473
Number of Shares
Granted (in shares)		3,473
2019 LTIP | Stock options | Non-executive members of management
Stock-Based Compensation
Shares authorized					483										483						483
Number of equal annual allotments in which awards will vest | installment															3
Exercise price (in dollar per share) | $ / shares					$ 99.38										$ 99.38						$ 99.38
2019 LTIP | Stock options | Executive officers and other members of management
Stock-Based Compensation
Shares granted	8,603
Number of equal annual allotments in which awards will vest | installment	3
Exercise price (in dollar per share) | $ / shares	$ 123.95
Number of Shares
Granted (in shares)	8,603
2019 LTIP | Stock options | Executive officers and other members of management | August 31, 2028 vesting date
Stock-Based Compensation
Shares forfeited	3,927
Number of Shares
Forfeited or cancelled (in shares)	(3,927)
2019 LTIP | Stock options | Executive officers and other members of management | September 1, 2028 Vesting date
Stock-Based Compensation
Shares forfeited	4,676
Number of Shares
Forfeited or cancelled (in shares)	(4,676)
2019 LTIP | Restricted stock
Stock-Based Compensation
Shares forfeited					833
Number of Shares
Forfeited or cancelled (in shares)					(833)
2019 LTIP | Performance and service based restricted stock | Executive officers and other members of management | August 31, 2021 vesting date
Stock-Based Compensation
Shares granted	3,541														211
Number of Shares
Granted (in shares)	3,541														211
2019 LTIP | Time-based restricted stock | Executive officers and other members of management | August 31, 2021 vesting date
Stock-Based Compensation
Shares granted	3,068														132
Number of Shares
Granted (in shares)	3,068														132