Goodwill and Intangible Assets - Components of Goodwill (Detail) - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Goodwill [Line Items]
Goodwill, Gross Amount	$ 22,264,000	$ 18,127,000
Goodwill, Accumulated Impairment Losses	5,055,000	5,055,000
Goodwill, Net	17,209,000	13,072,000
SLPE [Member]
Goodwill [Line Items]
Goodwill, Gross Amount	4,247,000	4,230,000
Goodwill, Net	4,247,000	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	4,773,000	653,000
Goodwill, Net	$ 4,773,000	$ 653,000