Goodwill and Intangible Assets - Components of Goodwill (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Goodwill [Line Items]
Goodwill, Gross Amount	$ 18,125,000us-gaap_GoodwillGross	$ 18,127,000us-gaap_GoodwillGross
Goodwill, Accumulated Impairment Losses	5,055,000	5,055,000
Goodwill, Net	13,070,000us-gaap_Goodwill	13,072,000us-gaap_Goodwill
SLPE [Member]
Goodwill [Line Items]
Goodwill, Gross Amount	4,228,000	4,230,000
Goodwill, Net	4,228,000	4,230,000
High Power Group [Member] \| MTE Corporation [Member]
Goodwill [Line Items]
Goodwill, Gross Amount	8,189,000	8,189,000
Goodwill, Net	8,189,000	8,189,000
High Power Group [Member] \| TEAL Electronics Corp. [Member]
Goodwill [Line Items]
Goodwill, Gross Amount	5,055,000	5,055,000
Goodwill, Accumulated Impairment Losses	5,055,000	5,055,000
SL-MTI [Member]
Goodwill [Line Items]
Goodwill, Gross Amount	653,000	653,000
Goodwill, Net	$ 653,000	$ 653,000

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a,h)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of accumulated impairment loss for an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

+ Details

Name:	us-gaap_GoodwillImpairedAccumulatedImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_GoodwillLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=sli_HighPowerGroupMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=sli_SLMTIMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=sli_SLPEMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: