Short-Term Borrowings (Details) - USD ($)			9 Months Ended
	Oct. 07, 2020	Mar. 13, 2020	Aug. 31, 2020	Nov. 30, 2019
Short-term Debt [Line Items]
Short-term borrowings			$ 805,381,000	$ 548,490,000
Interest rates on short-term borrowings outstanding			1.83%	3.24%
Floating rate puttable notes
Short-term Debt [Line Items]
Short-term borrowings			$ 6,800,000	$ 0
Principal amount of short-term debt issued			6,800,000
Equity-linked notes
Short-term Debt [Line Items]
Short-term borrowings			21,829,000	20,981,000
Principal amount of short-term debt issued			5,000,000.0
Short-term debt matured		$ 5,200,000
Equity-linked notes | Subsequent Event
Short-term Debt [Line Items]
Short-term debt matured	$ 15,100,000
Jefferies Group credit facility | Line of Credit | JPMorgan Chase Bank, N.A.
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity			246,000,000.0
RBC Credit Facility | Royal Bank of Canada
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity			$ 200,000,000.0
RBC Credit Facility | Royal Bank of Canada | LIBOR
Short-term Debt [Line Items]
Basis spread on variable rate (as a percent)			2.05%
Intraday Credit Facility | Revolving Credit Facility
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity			$ 150,000,000.0
Debt instrument, interest rate			0.12%
Intraday Credit Facility | Revolving Credit Facility | Base rate
Short-term Debt [Line Items]
Basis spread on variable rate (as a percent)			3.00%
Intraday Credit Facility | Revolving Credit Facility | Federal funds effective rate
Short-term Debt [Line Items]
Basis spread on variable rate (as a percent)			0.50%
Bank loans
Short-term Debt [Line Items]
Short-term borrowings			$ 776,752,000	$ 527,509,000