Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	May 31, 2019	Jun. 30, 2018	May 31, 2019	Jun. 30, 2018	Nov. 30, 2018
Private Equity Related Funds
Related Party Transaction [Line Items]
Loans to and/or equity investments in related funds	$ 31.2		$ 31.2		$ 35.5
Net gains (losses) from private equity related funds	4.0	$ 3.0	(0.1)	$ 10.0
Officers and Employees
Related Party Transaction [Line Items]
Loans outstanding to related party	46.9		46.9		49.3
Berkadia | Affiliated Entity | Jefferies Group
Related Party Transaction [Line Items]
Purchase commitment	543.4		543.4		723.8
FXCM | Payables, expense accruals and other liabilities | Affiliated Entity | Jefferies Group
Related Party Transaction [Line Items]
OTC foreign exchange contracts	$ 14.2		$ 14.2		$ 9.9