Stockholders' Equity - Stock Option Grants, Activity And Expense (Details) $ / shares in Units, $ in Thousands			3 Months Ended					9 Months Ended
	Mar. 09, 2020 USD ($) $ / shares shares	Mar. 03, 2020 $ / shares shares	Aug. 31, 2020 USD ($) individual $ / shares shares	Feb. 29, 2020 $ / shares shares	Aug. 31, 2019 USD ($) $ / shares shares	May 31, 2019	Feb. 28, 2019 $ / shares shares	Aug. 31, 2020 USD ($) individual $ / shares shares	Aug. 31, 2019 USD ($) $ / shares shares
2009 Stock Option Plan
Granted (in shares)								111,258	5,946
Exercise of stock options (shares)								44,900	29,838
Proceeds from exercise of stock options | $								$ 210	$ 98
Assumptions used in determining the fair value of the stock options granted
Expected volatility (as a percent)									30.90%
Risk free interest rates (as a percent)									2.30%
Expected option term (in years)								8 years 6 months	8 years 6 months
Annual dividend yield (as a percent)									1.20%
Other Disclosures
Number of option holders | individual			29					29
Unrecognized compensation expense related to non-vested stock options that will be recognized during future periods
Balance of Fiscal 2020 | $			$ 124					$ 124
Fiscal 2021 | $			442					442
Fiscal 2022 | $			377					377
Fiscal 2023 | $			244					244
Fiscal 2024 | $			120					120
Fiscal 2025 | $			$ 23					$ 23
Griffin's stock option activity
Outstanding at beginning of period (in shares)				189,822			224,001	189,822	224,001
Granted (in shares)								111,258	5,946
Exercised (in shares)								(44,900)	(29,838)
Forfeited (in shares)									(7,788)
Outstanding at end of period (in shares)			256,180		192,321			256,180	192,321
Weighted Avg. Exercise Price
Outstanding at beginning of period (in dollars per share) | $ / shares				$ 28.23			$ 28.20	$ 28.23	$ 28.20
Granted (in dollars per share) | $ / shares								45.72	36.99
Exercised (in dollars per share) | $ / shares								28.73	28.71
Forfeited (in dollars per share) | $ / shares									32.62
Outstanding at end of period (in dollars per share) | $ / shares			$ 35.74		$ 28.21			$ 35.74	$ 28.21
Minimum
Assumptions used in determining the fair value of the stock options granted
Expected volatility (as a percent)								29.70%
Risk free interest rates (as a percent)								0.50%
Annual dividend yield (as a percent)								1.30%
Maximum
Assumptions used in determining the fair value of the stock options granted
Expected volatility (as a percent)								30.30%
Risk free interest rates (as a percent)								0.90%
2009 Stock Option Plan
2009 Stock Option Plan
Expiration term								10 years
Number of options that may be exercised as stock appreciation rights			0					0
Granted (in shares)		48,000						0
Exercise price (in dollars per share) | $ / shares		$ 45.98
Compensation expense for stock options
Compensation expense (benefit) | $			$ 125		$ 21			$ 385	$ 205
Related tax benefit (expense) | $			$ 26		$ 9			$ 69	$ 35
Griffin's stock option activity
Granted (in shares)		48,000						0
2009 Stock Option Plan | Minimum
Compensation expense for stock options
Forfeiture rates (as a percent)				0.00%			0.00%
2009 Stock Option Plan | Minimum | Employee
Compensation expense for stock options
Forfeiture rates (as a percent)				38.30%		38.30%
2009 Stock Option Plan | Minimum | Executives
Compensation expense for stock options
Forfeiture rates (as a percent)				17.90%		17.90%
2009 Stock Option Plan | Maximum
Compensation expense for stock options
Forfeiture rates (as a percent)				2.00%		2.00%
2020 Incentive Award Plan
2009 Stock Option Plan
Number of shares authorized		300,000
Granted (in shares)		52,000
Exercise price (in dollars per share) | $ / shares	$ 46.91	$ 46.91
Exercise of stock options (shares)	53,293
Proceeds from exercise of stock options | $	$ 2,500
Griffin's stock option activity
Granted (in shares)		52,000
Exercised (in shares)	(53,293)
2020 Incentive Award Plan and 2009 Stock Option Plan | Non-employee directors
2009 Stock Option Plan
Granted (in shares)								111,258	5,946
Fair values of stock options granted (in dollars per share) | $ / shares									$ 12.87
Griffin's stock option activity
Granted (in shares)								111,258	5,946
2020 Incentive Award Plan and 2009 Stock Option Plan | Minimum
2009 Stock Option Plan
Fair values of stock options granted (in dollars per share) | $ / shares								$ 11.00
2020 Incentive Award Plan and 2009 Stock Option Plan | Maximum
2009 Stock Option Plan
Fair values of stock options granted (in dollars per share) | $ / shares								$ 14.17