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Nature of Operations (Details) $ in Millions			1 Months Ended	3 Months Ended		5 Months Ended	9 Months Ended
Nature of Operations (Details) $ in Millions	Oct. 01, 2018 USD ($)	Jun. 05, 2018 USD ($)	Apr. 30, 2018 USD ($)	Sep. 30, 2018 USD ($) director Dealership	Jun. 30, 2018 USD ($)	Jun. 04, 2018 USD ($)	Sep. 30, 2018 USD ($) director Dealership	Jul. 13, 2018	Jul. 12, 2018	Dec. 31, 2017
National Beef
Nature Of Operations [Line Items]
Percentage interest owned in subsidiary				100.00%			100.00%
Number of seats on investment committee retained by Company \| director				2			2
Lockup period related to divestiture of businesses							5 years
Marfrig Global Foods S.A.
Nature Of Operations [Line Items]
Percentage interest owned in subsidiary				51.00%			51.00%
Ownership percentage to be acquired further from other equity owners		3.00%
Garcadia
Nature Of Operations [Line Items]
Number of automobile dealerships \| Dealership				28			28
Vitesse Energy, LLC
Nature Of Operations [Line Items]
Payments to acquire productive assets, funded as equity			$ 144.0
Discontinued operations, disposed of by sale \| National Beef
Nature Of Operations [Line Items]
Percentage interest owned in subsidiary		48.00%
Cash from sale of subsidiary		$ 907.7
Pre-tax gain on disposal of discontinued operations							$ 873.5
Held-for-sale, not discontinued operations \| Garcadia
Nature Of Operations [Line Items]
Percentage of equity method investment for sale				100.00%
Proceeds from sale of equity method investments and associated real estate				$ 417.2
Pre-tax gain on sale of equity method investments and associated real estate				$ 221.7			$ 221.7
Package of Non-Operated Bakken Assets \| Vitesse Energy, LLC
Nature Of Operations [Line Items]
Payments to acquire Bakken assets			$ 190.0
HRG
Nature Of Operations [Line Items]
Percentage interest owned in subsidiary									23.00%	23.00%
National Beef
Nature Of Operations [Line Items]
Equity method investment, ownership percentage		31.00%		31.00%			31.00%
Percentage interest owned in subsidiary						79.00%
Weiss Multi-Strategy Advisors LLC
Nature Of Operations [Line Items]
Amount invested in asset management strategy					$ 250.0
Combined Strategy
Nature Of Operations [Line Items]
Equity commitments				$ 250.0			$ 250.0
Spectrum Brands
Nature Of Operations [Line Items]
Percentage interest owned in subsidiary				14.00%			14.00%	14.00%
Spectrum Brands \| HRG
Nature Of Operations [Line Items]
Percentage interest owned in subsidiary								62.00%
National Beef
Nature Of Operations [Line Items]
Additional proceeds expected from divestiture of businesses						$ 229.4
Subsequent Event [Member]
Nature Of Operations [Line Items]
Capital contributed	$ 596.0
Jefferies Group \| Affiliated Entity \| Subsequent Event [Member]
Nature Of Operations [Line Items]
Proceeds from related party transfer	$ 78.3