Revenues from Contracts with Customers (Disaggregation of Revenue) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	$ 2,508,047
Americas
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	2,203,492
Europe, Middle East and Africa
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	79,179
Asia
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	225,376
Reportable Segments | Jefferies
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	599,509
Reportable Segments | Jefferies | Americas
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	520,854
Reportable Segments | Jefferies | Europe, Middle East and Africa
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	61,328
Reportable Segments | Jefferies | Asia
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	17,327
Reportable Segments | National Beef
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	1,779,631
Reportable Segments | National Beef | Americas
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	1,554,061
Reportable Segments | National Beef | Europe, Middle East and Africa
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	17,596
Reportable Segments | National Beef | Asia
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	207,974
Reportable Segments | Corporate and other
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	8,233
Reportable Segments | Corporate and other | Americas
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	7,903
Reportable Segments | Corporate and other | Europe, Middle East and Africa
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	255
Reportable Segments | Corporate and other | Asia
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	75
All other
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	120,674
All other | Americas
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	120,674
All other | Europe, Middle East and Africa
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
All other | Asia
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
Equities
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	151,630
Equities | Reportable Segments | Jefferies
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	151,630
Fixed Income
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	2,958
Fixed Income | Reportable Segments | Jefferies
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	2,958
Investment banking
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	439,991
Investment banking | Reportable Segments | Jefferies
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	439,991
Asset Management
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	4,930
Asset Management | Reportable Segments | Jefferies
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	4,930
Beef processing services
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	1,779,631
Beef processing services | Reportable Segments | Jefferies
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
Beef processing services | Reportable Segments | National Beef
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	1,779,631
Beef processing services | Reportable Segments | Corporate and other
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
Beef processing services | All other
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
Manufacturing revenues
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	98,365
Manufacturing revenues | Reportable Segments | Jefferies
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
Manufacturing revenues | Reportable Segments | National Beef
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
Manufacturing revenues | Reportable Segments | Corporate and other
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
Manufacturing revenues | All other
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	98,365
Oil and gas revenues
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	20,330
Oil and gas revenues | Reportable Segments | Jefferies
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
Oil and gas revenues | Reportable Segments | National Beef
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
Oil and gas revenues | Reportable Segments | Corporate and other
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
Oil and gas revenues | All other
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	20,330
Other revenues
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	10,212
Other revenues | Reportable Segments | Jefferies
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
Other revenues | Reportable Segments | National Beef
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	0
Other revenues | Reportable Segments | Corporate and other
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	8,233
Other revenues | All other
Disaggregation Of Revenue [Line Items]
Revenue from contracts with customers	$ 1,979