Revised Financial Statements - Statement of Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended									6 Months Ended
		Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2015	Jun. 30, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)		$ (10,463)			$ 7,657						$ (18,076)	$ 9,624
Foreign currency translation adjustment		(3)			14						(1)	14
Reclassification to realized gains		0			0						0	0
Net foreign currency translation adjustment	[1]	(3)			14						(1)	14
Gross unrealized gains on marketable securities, net of tax	[2]	1,950			3,395						3,064	11,418
Reclassification to realized gains, net of tax	[3]	12,239			(505)						12,054	(2,439)
Net unrealized gain on marketable securities, net of tax		14,189			2,890						15,118	8,979
Comprehensive income (loss)		3,723			10,561						(2,959)	18,617
Comprehensive loss (income) attributable to non-controlling interest		(73)			11						290	337
Comprehensive income (loss) attributable to Steel Excel Inc.		3,650			10,572						(2,669)	18,954
Tax provision on gross unrealized gains		(1,159)			0						(1,707)	0
Tax benefit on reclassifications to realized gains (losses)		$ (6,809)			0						$ (6,718)	0
Valuation Allowance of Deferred Tax Assets
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)			$ (33,462)	$ 75	7,657	$ 1,967	$ 4,087	$ 1,495	$ 538	$ 1,207		9,624
Foreign currency translation adjustment					14							14
Reclassification to realized gains					0							0
Net foreign currency translation adjustment					14							14
Gross unrealized gains on marketable securities, net of tax					3,395							11,418
Reclassification to realized gains, net of tax					(505)							(2,439)
Net unrealized gain on marketable securities, net of tax					2,890							8,979
Comprehensive income (loss)					10,561							18,617
Comprehensive loss (income) attributable to non-controlling interest					11							337
Comprehensive income (loss) attributable to Steel Excel Inc.					10,572							18,954
Tax provision on gross unrealized gains					0							0
Tax benefit on reclassifications to realized gains (losses)					0							0
Valuation Allowance of Deferred Tax Assets | Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)					8,732							12,797
Foreign currency translation adjustment					14							14
Reclassification to realized gains					0							0
Net foreign currency translation adjustment					14							14
Gross unrealized gains on marketable securities, net of tax					2,124							7,383
Reclassification to realized gains, net of tax					(309)							(1,577)
Net unrealized gain on marketable securities, net of tax					1,815							5,806
Comprehensive income (loss)					10,561							18,617
Comprehensive loss (income) attributable to non-controlling interest					11							337
Comprehensive income (loss) attributable to Steel Excel Inc.					10,572							18,954
Tax provision on gross unrealized gains					1,271							(4,035)
Tax benefit on reclassifications to realized gains (losses)					196							862
Valuation Allowance of Deferred Tax Assets | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)					(1,075)							(3,173)
Foreign currency translation adjustment					0							0
Reclassification to realized gains					0							0
Net foreign currency translation adjustment					0							0
Gross unrealized gains on marketable securities, net of tax					1,271							4,035
Reclassification to realized gains, net of tax					(196)							(862)
Net unrealized gain on marketable securities, net of tax					1,075							3,173
Comprehensive income (loss)					0							0
Comprehensive loss (income) attributable to non-controlling interest					0							0
Comprehensive income (loss) attributable to Steel Excel Inc.					0							0
Tax provision on gross unrealized gains					(1,271)							4,035
Tax benefit on reclassifications to realized gains (losses)					$ (196)							$ (862)

[1] No tax effect on cumulative translation adjustments

[2] Tax provision on gross unrealized gains: $(1,159) $0 $(1,707) $0

[3] Tax benefit on reclassifications to realized gains: $(6,809) $0 $(6,718) $0