Retirement Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Nov. 30, 2016	Nov. 30, 2015	Nov. 30, 2014	Feb. 28, 2014
Change in benefit obligation:
Curtailment gain			$ (309)
Savings Plan
401(k) Savings Plan
Employer matching contribution, as a percentage of employee contribution	60.00%
Contributions to the Griffin Savings Plan	$ 64	$ 60	64
Savings Plan | Maximum
401(k) Savings Plan
Employer matching contribution as a percentage of base salary	5.00%
Deferred Compensation Plan
Deferred Compensation Plan
Liability under Deferred Compensation Plan	$ 4,334	3,981
Expense for employer matching benefit to the Deferred Compensation Plan	$ 7	$ 22	28
Postretirement benefits, life and health
Deferred Compensation Plan
Benefit obligation			332	$ 23
Change in benefit obligation:
Benefit obligation at beginning of year			332
Actuarial (gain) loss			(14)
Interest cost			4
Service cost			1
Amortization of actuarial gain			(14)
Curtailment gain			309
Components of postretirement benefits expense (income)
Service cost			1
Interest			4
Amortization of actuarial gain			(14)
Total income			(318)
Other changes in benefit obligations recognized in other comprehensive loss:
Actuarial gain			(14)
Total recognized in net periodic benefit income and other comprehensive loss			$ (332)
Discount rate
Discount rate used to compute accumulated postretirement benefit obligations (as a percent)			4.60%
Discount rates used to compute net periodic benefit expense (as a percent)			4.60%