Schedule I - Condensed Financial Information of Registrant - Condensed Statements of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other comprehensive income (loss):
Net unrealized holding gains (losses) on investments arising during the period, net of income tax provision (benefit) of $3,450, $2,262 and $(5,029)									$ 5,923	$ 3,900	$ (9,057)
Less: reclassification adjustment for net (gains) losses included in net income, net of income tax provision (benefit) of $124, $2 and $6,068									(212)	(4)	(10,930)
Net change in unrealized holding gains (losses) on investments, net of income tax provision (benefit) of $3,326, $2,260 and $(11,097)									5,711	3,896	(19,987)
Net unrealized foreign exchange gains (losses) arising during the period, net of income tax provision (benefit) of $14,616, $(3,530) and $(5,174)									78,493	(121,581)	(36,477)
Less: reclassification adjustment for foreign exchange (gains) losses included in net income, net of income tax provision (benefit) of $1,086, $0 and $0									5,310	0	0
Net change in unrealized foreign exchange gains (losses), net of income tax provision (benefit) of $13,530, $(3,530) and $(5,174)									83,803	(121,581)	(36,477)
Net unrealized gains (losses) on instrument specific credit risk arising during the period, net of income tax provision (benefit) of $(13,215), $(4,251) and $0									(21,394)	(6,494)	0
Net change in unrealized instrument specific credit risk gains (losses), net of income tax provision (benefit) of $(13,215), $(4,251) and $0									(21,394)	(6,494)	0
Net unrealized gains (losses) on cash flow hedges arising during the period, net of income tax provision (benefit) of $(593), $0 and $0									(936)	0	0
Net change in unrealized cash flow hedges gains (losses), net of income tax provision (benefit) of $(593), $0 and $0									(936)	0	0
Net pension gains (losses) arising during the period, net of income tax provision (benefit) of $2,018, $(2,516) and $7,152									3,526	(5,451)	17,073
Less: reclassification adjustment for pension (gains) losses included in net income, net of income tax provision (benefit) of $(2,042), $(700) and $(17,159)									517	1,534	31,102
Net change in pension liability benefits, net of income tax provision (benefit) of $4,060, $(1,816) and $24,311									4,043	(3,917)	48,175
Other comprehensive income (loss), net of income taxes									71,227	(128,096)	(8,289)
Preferred stock dividends	$ (1,172)	$ (1,172)	$ (1,015)	$ (1,016)	$ (1,016)	$ (1,016)	$ (1,015)	$ (1,016)	(4,375)	(4,063)	(4,063)
Comprehensive income (loss) attributable to Leucadia National Corporation common shareholders									238,578	(2,158)	271,298
Parent Company
Condensed Statement of Income Captions [Line Items]
Net income									171,726	130,001	283,650
Other comprehensive income (loss):
Net unrealized holding gains (losses) on investments arising during the period, net of income tax provision (benefit) of $3,450, $2,262 and $(5,029)									5,923	3,900	(9,057)
Less: reclassification adjustment for net (gains) losses included in net income, net of income tax provision (benefit) of $124, $2 and $6,068									(212)	(4)	(10,930)
Net change in unrealized holding gains (losses) on investments, net of income tax provision (benefit) of $3,326, $2,260 and $(11,097)									5,711	3,896	(19,987)
Net unrealized foreign exchange gains (losses) arising during the period, net of income tax provision (benefit) of $14,616, $(3,530) and $(5,174)									78,493	(121,581)	(36,477)
Less: reclassification adjustment for foreign exchange (gains) losses included in net income, net of income tax provision (benefit) of $1,086, $0 and $0									5,310	0	0
Net change in unrealized foreign exchange gains (losses), net of income tax provision (benefit) of $13,530, $(3,530) and $(5,174)									83,803	(121,581)	(36,477)
Net unrealized gains (losses) on instrument specific credit risk arising during the period, net of income tax provision (benefit) of $(13,215), $(4,251) and $0									(21,394)	(6,494)	0
Net change in unrealized instrument specific credit risk gains (losses), net of income tax provision (benefit) of $(13,215), $(4,251) and $0									(21,394)	(6,494)	0
Net unrealized gains (losses) on cash flow hedges arising during the period, net of income tax provision (benefit) of $(593), $0 and $0									(936)	0	0
Net change in unrealized cash flow hedges gains (losses), net of income tax provision (benefit) of $(593), $0 and $0									(936)	0	0
Net pension gains (losses) arising during the period, net of income tax provision (benefit) of $2,018, $(2,516) and $7,152									3,526	(5,451)	17,073
Less: reclassification adjustment for pension (gains) losses included in net income, net of income tax provision (benefit) of $(2,042), $(700) and $(17,159)									517	1,534	31,102
Net change in pension liability benefits, net of income tax provision (benefit) of $4,060, $(1,816) and $24,311									4,043	(3,917)	48,175
Other comprehensive income (loss), net of income taxes									71,227	(128,096)	(8,289)
Comprehensive income									242,953	1,905	275,361
Preferred stock dividends									(4,375)	(4,063)	(4,063)
Comprehensive income (loss) attributable to Leucadia National Corporation common shareholders									$ 238,578	$ (2,158)	$ 271,298