Common Shares and Earnings Per Common Share - Earnings Per Share Computation (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
Numerator for earnings per share:
Net income attributable to Leucadia National Corporation common shareholders	$ (271,601)	$ 99,351	$ 58,193	$ 281,408	$ 137,171	$ 154,358	$ 57,289	$ (222,880)	$ 167,351	$ 125,938	$ 279,587
Allocation of earnings to participating securities									(610)	(574)	(4,711)
Net income attributable to Leucadia National Corporation common shareholders for basic earnings per share									166,741	125,364	274,876
Adjustment to allocation of earnings to participating securities related to diluted shares									(14)	(19)	(34)
Mandatorily redeemable convertible preferred share dividends									0	0	0
Net income attributable to Leucadia National Corporation common shareholders for diluted earnings per share									$ 166,727	$ 125,345	$ 274,842
Denominator for earnings per share:
Denominator for basic earnings per share – weighted average shares (shares)	366,000,000	367,828,000	369,212,000	369,267,000	369,299,000	370,404,000	372,556,000	372,367,000	368,197,000	371,211,000	372,430,000
Mandatorily redeemable convertible preferred shares (shares)									0	0	0
Denominator for diluted earnings per share (shares)	366,000,000	370,198,000	371,552,000	375,721,000	374,693,000	374,567,000	372,556,000	372,367,000	370,701,000	371,518,000	372,431,000
Weighted average shares of participating securities									1,401,000	1,986,800	6,500,000
Dividends declared on participating securities									$ 400	$ 400	$ 1,500
Stock options
Denominator for earnings per share:
Dilutive effect of share-based payment arrangements (shares)									24,000	0	1,000
Restricted Stock Units (RSUs)
Denominator for earnings per share:
Dilutive effect of share-based payment arrangements (shares)									2,480,000	307,000	0