Industry Segments - Capital Expenditures by Segment (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Capital expenditures
Capital Expenditures	$ 1,804,000	$ 2,690,000	$ 1,416,000
SLPE [Member]
Capital expenditures
Capital Expenditures	386,000	1,660,000	492,000
High Power Group [Member]
Capital expenditures
Capital Expenditures	613,000	275,000	440,000
SL-MTI [Member]
Capital expenditures
Capital Expenditures	549,000	512,000	258,000
RFL [Member]
Capital expenditures
Capital Expenditures	251,000	224,000	226,000
Unallocated Corporate Expenses [Member]
Capital expenditures
Capital Expenditures	$ 5,000	$ 19,000