Loans to and Investments in Associated Companies (Jefferies Finance, Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2020	Aug. 31, 2019	Nov. 30, 2019	Mar. 28, 2019
Investments In Associated Companies [Line Items]
Other assets	$ 2,375,171,000		$ 2,375,171,000		$ 2,450,109,000
Payables, expense accruals and other liabilities	8,792,748,000		8,792,748,000		8,179,013,000
Interest expense	21,512,000	$ 23,663,000	64,226,000	$ 69,819,000
Jefferies Finance
Investments In Associated Companies [Line Items]
Equity commitment	750,000,000.0		750,000,000.0
Funded equity commitments	652,400,000		$ 652,400,000
Investment commitment extension			1 year
Investment commitment termination notice period			60 days
Total line of credit facility commitment under joint venture	500,000,000.0		$ 500,000,000.0
Termination notice			60 days
Line of credit facility, commitment of Jefferies, funded	0.0		$ 0.0
Line of credit facility commitment of Jefferies	250,000,000.0		250,000,000.0
Jefferies Group
Investments In Associated Companies [Line Items]
Interest expense	$ 209,329,000	366,378,000	$ 745,207,000	1,141,661,000
Jefferies Group | Promissory Note
Investments In Associated Companies [Line Items]
Debt principal amount						$ 1,000,000,000.0
Interest expense				3,800,000
Jefferies Finance
Investments In Associated Companies [Line Items]
Equity method investment, ownership percentage	50.00%		50.00%
Extension period			1 year
Other assets	$ 13,200,000		$ 13,200,000		17,200,000
Payables, expense accruals and other liabilities	13,700,000		13,700,000		13,700,000
Jefferies Finance | Lending Transactions
Investments In Associated Companies [Line Items]
Payables, expense accruals and other liabilities					$ 17,600,000
Jefferies Finance | Jefferies Group
Investments In Associated Companies [Line Items]
Interest income and unfunded commitment fees related to facility commitment	$ 400,000	$ 300,000	$ 3,000,000.0	$ 900,000