Unaudited Quarterly Financial Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Operating revenues:
Operating revenues	$ 11,193	$ 11,324	$ 9,340	$ 12,076	$ 9,386	$ 7,587	$ 1,199	$ 1,336	$ 43,933	$ 19,508
Operating costs	10,256	12,640	12,212	11,244	12,449	10,193	4,290	2,744	46,352	29,676
Operating loss	937	(1,316)	(2,872)	832	(3,063)	(2,606)	(3,091)	(1,408)	(2,419)	(10,168)
Earnings (loss) from continuing operations	718	(2,166)	(3,158)	639	(2,589)	4,133	(3,916)	(1,095)	(3,967)	(3,467)
Loss from discontinued operations, net of income taxes	(422)	(462)	(732)	(1,885)	(1,094)	(2,889)	(2,358)	(3,066)	(3,501)	(9,407)
Net earnings (loss) attributable to Signature Group Holdings, Inc.	296	(2,628)	(3,890)	(1,246)	(3,675)	1,275	(6,173)	(4,201)	(7,468)	(12,774)
Basic and diluted earnings (loss) per share:
Continuing operations	$ 0.01	$ (0.02)	$ (0.02)	$ 0.01	$ (0.02)	$ 0.04	$ (0.03)	$ (0.01)	$ (0.03)	$ (0.03)
Discontinued operations	$ (0.01)		$ (0.01)	$ (0.02)	$ (0.01)	$ (0.03)	$ (0.02)	$ (0.03)	$ (0.03)	$ (0.08)
Basic and diluted earnings (loss) per share		$ (0.02)	$ (0.03)	$ (0.01)	$ (0.03)	$ 0.01	$ (0.05)	$ (0.04)	$ (0.06)	$ (0.11)
Industrial Supply
Operating revenues:
Operating revenues	9,134	10,203	9,062	7,843	8,076	6,082
Signature Special Situations
Operating revenues:
Operating revenues	$ 2,059	$ 1,121	$ 278	$ 4,233	$ 1,310	$ 1,505	$ 1,199	$ 1,336