Industry Segments - Depreciation and Amortization by Segment (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Depreciation and amortization
Depreciation and amortization	$ 2,711,000	$ 2,870,000	$ 3,026,000
SLPE [Member]
Depreciation and amortization
Depreciation and amortization	926,000	1,207,000	1,381,000
High Power Group [Member]
Depreciation and amortization
Depreciation and amortization	926,000	856,000	831,000
SL-MTI [Member]
Depreciation and amortization
Depreciation and amortization	431,000	309,000	302,000
RFL [Member]
Depreciation and amortization
Depreciation and amortization	415,000	473,000	465,000
Unallocated Corporate Expenses [Member]
Depreciation and amortization
Depreciation and amortization	$ 13,000	$ 25,000	$ 47,000