Revised Financial Statements - Statement of Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended									9 Months Ended
		Sep. 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	Sep. 30, 2015	Sep. 30, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)		$ (14,263)		$ 75							$ (32,339)	$ 9,699
Foreign currency translation adjustment		(5)		16							(6)	30
Reclassification to realized gains		0		0							0	0
Net foreign currency translation adjustment	[1]	(5)		16							(6)	30
Gross unrealized gains on marketable securities, net of tax	[2]	(5,871)		(1,347)							(2,807)	10,071
Reclassification to realized gains, net of tax	[3]	(567)		(1,345)							11,487	(3,784)
Net unrealized gain (loss) on marketable securities, net of tax		(6,438)		(2,692)							8,680	6,287
Comprehensive income (loss)		(20,706)		(2,601)							(23,665)	16,016
Comprehensive loss (income) attributable to non-controlling interest		(211)		(238)							79	99
Comprehensive income (loss) attributable to Steel Excel Inc.		(20,917)		(2,839)							(23,586)	16,115
Tax benefit on gross unrealized gains		3,279		0							1,572	0
Tax benefit on reclassifications to realized gains (losses)		$ 284		0							$ (6,434)	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		9,699
Foreign currency translation adjustment				16								30
Reclassification to realized gains				0								0
Net foreign currency translation adjustment				16								30
Gross unrealized gains on marketable securities, net of tax				(1,347)								10,071
Reclassification to realized gains, net of tax				(1,345)								(3,784)
Net unrealized gain (loss) on marketable securities, net of tax				(2,692)								6,287
Comprehensive income (loss)				(2,601)								16,016
Comprehensive loss (income) attributable to non-controlling interest				(238)								99
Comprehensive income (loss) attributable to Steel Excel Inc.				(2,839)								16,115
Tax benefit 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)				(945)								11,852
Foreign currency translation adjustment				16								30
Reclassification to realized gains				0								0
Net foreign currency translation adjustment				16								30
Gross unrealized gains on marketable securities, net of tax				(761)								6,622
Reclassification to realized gains, net of tax				(911)								(2,488)
Net unrealized gain (loss) on marketable securities, net of tax				(1,672)								4,134
Comprehensive income (loss)				(2,601)								16,016
Comprehensive loss (income) attributable to non-controlling interest				(238)								99
Comprehensive income (loss) attributable to Steel Excel Inc.				(2,839)								16,115
Tax benefit on gross unrealized gains				(586)								(3,449)
Tax benefit on reclassifications to realized gains (losses)				434								1,296
Valuation Allowance of Deferred Tax Assets | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)				1,020								(2,153)
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				(586)								3,449
Reclassification to realized gains, net of tax				(434)								(1,296)
Net unrealized gain (loss) on marketable securities, net of tax				(1,020)								2,153
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 benefit on gross unrealized gains				586								3,449
Tax benefit on reclassifications to realized gains (losses)				$ (434)								$ (1,296)

[1] No tax effect on cumulative translation adjustments

[2] Tax provision on gross unrealized gains: $3,279 $0 $1,572 $0

[3] Tax benefit on reclassifications to realized gains: $284 $0 $(6,434) $0