Related Party Transactions (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Nov. 30, 2019	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2020	Aug. 31, 2019
Private Equity Related Funds
Related Party Transaction [Line Items]
Loans to and/or equity investments in related funds	$ 23.0	$ 18.6		$ 18.6
JCP Fund V
Related Party Transaction [Line Items]
Net gains (losses) from private equity related funds		2.0	$ (2.5)	(3.5)	$ (1.9)
Officers and Employees
Related Party Transaction [Line Items]
Loans outstanding to related party	44.8	40.8		40.8
Berkadia | Affiliated Entity | Jefferies Group
Related Party Transaction [Line Items]
Purchase commitment	360.4	325.6		325.6
Jefferies Finance | Affiliated Entity
Related Party Transaction [Line Items]
Purchases of loan receivables	65.3
Payables, expense accruals and other liabilities | FXCM | Affiliated Entity | Jefferies Group
Related Party Transaction [Line Items]
OTC foreign exchange contracts	$ 9.9	$ 2.7		$ 2.7