Stockholders' Equity (Details)						1 Months Ended										3 Months Ended								12 Months Ended
	Sep. 01, 2019 installment $ / shares shares	Sep. 01, 2018 installment $ / shares shares	Sep. 01, 2017 $ / shares shares	Sep. 01, 2016 installment shares	Sep. 01, 2015 shares	May 31, 2020 shares	Feb. 29, 2020 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	Aug. 31, 2015 installment $ / shares shares	Aug. 31, 2020 individual item $ / shares shares	Feb. 29, 2020 shares	Aug. 31, 2019 installment $ / shares shares	Aug. 31, 2018 $ / shares shares	May 31, 2018 installment $ / shares shares	Nov. 30, 2016 shares	Nov. 30, 2015 shares	May 31, 2015 shares	Aug. 31, 2020 individual item $ / shares shares	Aug. 31, 2019 $ / shares shares	Aug. 31, 2018 $ / shares shares	Aug. 31, 2017 $ / shares shares	Oct. 31, 2012 shares	Nov. 30, 2005 shares
Non-employee members of BOD
Stock-Based Compensation
Shares granted																								4,906	4,599	2,779
Number of Shares
Unvested restricted stock, beginning balance (in shares)	4,599	2,779	2,407							2,779														4,599	2,779	2,407
Granted (in shares)																								4,906	4,599	2,779
Vested (in shares)																								(4,599)	(2,779)	(2,407)
Unvested restricted stock, ending balance (in shares)								4,599				2,407				4,906		4,599	2,779					4,906	4,599	2,779	2,407
Weighted Average Grant Date Fair Value
Unvested restricted stock, beginning balance (in dollars per share) | $ / shares	$ 101.92	$ 101.05	$ 91.05							$ 101.05														$ 101.92	$ 101.05	$ 91.05
Granted (in dollars per share) | $ / shares																								95.59	101.92	101.05
Vested (in dollars per share) | $ / shares																								101.92	101.05	91.05
Unvested restricted stock, ending balance (in dollars per share) | $ / shares								$ 101.92				$ 91.05				$ 95.59		$ 101.92	$ 101.05					$ 95.59	$ 101.92	$ 101.05	$ 91.05
Officers and employees
Stock-Based Compensation
Shares granted																								43,841	7,524	13,922
Weighted Average Exercise Price (in dollars per share) | $ / shares																57.96								$ 57.96
Shares forfeited																								3,126	3,305
Exercise price (in dollar per share) | $ / shares								$ 57.18				$ 34.21				$ 75.21		$ 57.18	$ 50.17					$ 75.21	$ 57.18	$ 50.17	$ 34.21
Number of Shares
Unvested restricted stock, beginning balance (in shares)	44,355	65,579	73,972							65,579														44,355	65,579	73,972
Granted (in shares)																								43,841	7,524	13,922
Vested (in shares)																								(25,195)	(25,443)	(22,315)
Forfeited or cancelled (in shares)																								(3,126)	(3,305)
Unvested restricted stock, ending balance (in shares)								44,355				73,972				59,875		44,355	65,579					59,875	44,355	65,579	73,972
Weighted Average Grant Date Fair Value
Unvested restricted stock, beginning balance (in dollars per share) | $ / shares	$ 67.18	$ 61.85	$ 51.56							$ 61.85														$ 67.18	$ 61.85	$ 51.56
Granted (in dollars per share) | $ / shares																								108.47	121.64	83.65
Vested (in dollars per share) | $ / shares																								61.51	65.79	41.35
Forfeited or cancelled (in dollars per share) | $ / shares																								123.19	79.39
Unvested restricted stock, ending balance (in dollars per share) | $ / shares								$ 67.18				$ 51.56				$ 97.72		$ 67.18	$ 61.85					97.72	$ 67.18	$ 61.85	$ 51.56
Stock options
Stock-Based Compensation
Common stock available for future issuance (in shares)								949,398										949,398							949,398
Weighted Average Exercise Price (in dollars per share) | $ / shares																$ 57.96								$ 57.96
Stock options | Executive officers and other members of management
Stock-Based Compensation
Number of equal annual installments | installment	3
Stock options | Executive officers | August 31, 2019 vesting date
Stock-Based Compensation
Shares authorized														23,563
Exercise price (in dollar per share) | $ / shares														$ 64.37
Restricted stock
Stock-Based Compensation
Shares forfeited										2,472														2,694
Number of Shares
Forfeited or cancelled (in shares)										(2,472)														(2,694)
Restricted stock | Non-executive members of management
Stock-Based Compensation
Number of grants | item																2								2
Number of non-executive members of management | individual																2								2
Shares forfeited						432
Number of Shares
Forfeited or cancelled (in shares)						(432)
Restricted stock | Non-executive members of management | July 27, 2021 vesting date
Stock-Based Compensation
Shares granted																481
Number of Shares
Granted (in shares)																481
Restricted stock | Non-executive members of management | June 15, 2021 vesting date
Stock-Based Compensation
Shares granted																261
Number of Shares
Granted (in shares)																261
Restricted stock | Non-employee members of BOD
Stock-Based Compensation
Shares granted							4,906		4,599		2,779		2,407
Vesting period							12 months		12 months		12 months		12 months
Number of Shares
Granted (in shares)							4,906		4,599		2,779		2,407
Time-based restricted stock | Executive officers
Stock-Based Compensation
Shares granted				16,312
Number of equal annual installments | installment				5
Vesting period				5 years
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)																949,398								949,398
2005 Incentive Plan
Stock-Based Compensation
Shares authorized																													1,000,000
Common stock available for future issuance (in shares)																39,473								39,473
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
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
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
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
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
2020 LTIP | Stock options | Executive officers and other members of management
Stock-Based Compensation
Shares authorized	13,418
Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 100.22
Stock options expiring earlier (in shares)	6,218
Stock options expiring later (in shares)	7,200
2020 LTIP | Restricted stock | Non-executive members of management | December 31 2021 vesting date
Stock-Based Compensation
Shares granted																	432,616
Number of Shares
Granted (in shares)																	432,616
2020 LTIP | Restricted stock | Non-executive members of management | December 31 2022 vesting date
Stock-Based Compensation
Shares granted																	18,720
Number of Shares
Granted (in shares)																	18,720
2020 LTIP | Restricted stock | Non-executive members of management | December 31 2024 vesting date
Stock-Based Compensation
Shares granted																	19,768
Number of Shares
Granted (in shares)																	19,768
2020 LTIP | Performance and service based restricted stock | Executive officers and other members of management | August 31, 2022 vesting date
Stock-Based Compensation
Shares granted	3,697
Number of Shares
Granted (in shares)	3,697
2020 LTIP | Time-based restricted stock | Executive officers and other members of management | August 31, 2022 vesting date
Stock-Based Compensation
Shares granted	3,689
Number of Shares
Granted (in shares)	3,689
Equity Retention Agreement | Stock options | Executive officers | August 31, 2022 vesting date
Stock-Based Compensation
Shares authorized	53,642
Exercise price (in dollar per share) | $ / shares	$ 100.22
Equity Retention Agreement | Time-based restricted stock | Executive officers | August 31, 2022 vesting date
Stock-Based Compensation
Shares granted	15,945
Number of Shares
Granted (in shares)	15,945