Long-Term Debt (Schedule Of Indebtedness) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	May 31, 2019	Jun. 30, 2018	May 31, 2019	Jun. 30, 2018	Nov. 30, 2018
Debt Instrument [Line Items]
Long-term debt	$ 7,860,984		$ 7,860,984		$ 7,617,563
Gain (loss) associated with an interest rate swap based on its designation as a fair value hedge	$ (1,009)	$ 139	$ (1,978)	$ 1,633
8.50% Senior Notes, due July 15, 2019
Debt Instrument [Line Items]
Interest rate	8.50%		8.50%
Parent Company
Debt Instrument [Line Items]
Long-term debt	$ 990,737		$ 990,737		990,116
Parent Company | 5.50% Senior Notes due October 18, 2023
Debt Instrument [Line Items]
Long-term debt	$ 743,993		$ 743,993		$ 743,397
Interest rate	5.50%		5.50%		5.50%
Principal Outstanding	$ 750,000		$ 750,000		$ 750,000
Parent Company | 6.625% Senior Notes due October 23, 2043
Debt Instrument [Line Items]
Long-term debt	$ 246,744		$ 246,744		$ 246,719
Interest rate	6.625%		6.625%		6.625%
Principal Outstanding	$ 250,000		$ 250,000		$ 250,000
Subsidiaries
Debt Instrument [Line Items]
Long-term debt	6,870,247		6,870,247		6,627,447
Subsidiaries | 8.50% Senior Notes, due July 15, 2019
Debt Instrument [Line Items]
Long-term debt	$ 648,382		$ 648,382		$ 699,659
Interest rate	8.50%		8.50%		8.50%
Principal Outstanding	$ 644,800		$ 644,800		$ 680,800
Subsidiaries | 2.375% Euro Medium Term Notes, due May 20, 2020
Debt Instrument [Line Items]
Long-term debt	$ 557,926		$ 557,926		$ 564,702
Interest rate	2.375%		2.375%		2.375%
Principal Outstanding	$ 558,450		$ 558,450		$ 565,500
Subsidiaries | 6.875% Senior Notes, due April 15, 2021
Debt Instrument [Line Items]
Long-term debt	$ 783,370		$ 783,370		$ 791,814
Interest rate	6.875%		6.875%		6.875%
Principal Outstanding	$ 750,000		$ 750,000		$ 750,000
Subsidiaries | 2.25% Euro Medium Term Notes, due July 13, 2022
Debt Instrument [Line Items]
Long-term debt	$ 4,225		$ 4,225		$ 4,243
Interest rate	2.25%		2.25%		2.25%
Principal Outstanding	$ 4,468		$ 4,468		$ 4,524
Subsidiaries | 5.125% Senior Notes, due January 20, 2023
Debt Instrument [Line Items]
Long-term debt	$ 611,492		$ 611,492		$ 612,928
Interest rate	5.125%		5.125%		5.125%
Principal Outstanding	$ 600,000		$ 600,000		$ 600,000
Subsidiaries | 4.85% Senior Notes, due January 15, 2027
Debt Instrument [Line Items]
Long-term debt	$ 753,509		$ 753,509		$ 709,484
Interest rate	4.85%		4.85%		4.85%
Principal Outstanding	$ 750,000		$ 750,000		$ 750,000
Subsidiaries | 6.45% Senior Debentures, due June 8, 2027
Debt Instrument [Line Items]
Long-term debt	$ 372,563		$ 372,563		$ 373,669
Interest rate	6.45%		6.45%		6.45%
Principal Outstanding	$ 350,000		$ 350,000		$ 350,000
Subsidiaries | 4.15% Senior Notes, due January 23, 2030
Debt Instrument [Line Items]
Long-term debt	$ 988,220		$ 988,220		$ 987,788
Interest rate	4.15%		4.15%		4.15%
Principal Outstanding	$ 1,000,000		$ 1,000,000		$ 1,000,000
Subsidiaries | 6.25% Senior Debentures, due January 15, 2036
Debt Instrument [Line Items]
Long-term debt	$ 511,464		$ 511,464		$ 511,662
Interest rate	6.25%		6.25%		6.25%
Principal Outstanding	$ 500,000		$ 500,000		$ 500,000
Subsidiaries | 6.50% Senior Notes, due January 20, 2043
Debt Instrument [Line Items]
Long-term debt	$ 420,435		$ 420,435		$ 420,625
Interest rate	6.50%		6.50%		6.50%
Principal Outstanding	$ 400,000		$ 400,000		$ 400,000
Subsidiaries | Structured Notes
Debt Instrument [Line Items]
Long-term debt	819,509		819,509		686,170
Subsidiaries | Foursight Capital Credit Facilities
Debt Instrument [Line Items]
Long-term debt	123,579		123,579		0
Subsidiaries | Other
Debt Instrument [Line Items]
Long-term debt	86,756		86,756		81,164
Jefferies Group | Subsidiaries | Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt	$ 188,817		188,817		$ 183,539
Interest rate swaps | Subsidiaries | 4.85% Senior Notes, due January 15, 2027
Debt Instrument [Line Items]
Gain (loss) associated with an interest rate swap based on its designation as a fair value hedge			$ (43,800)	$ 22,800