Segment Information - Total Assets by Segment (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Total assets
Total assets	$ 125,542,000	$ 131,776,000
Operating Segments [Member] | SLPE [Member]
Total assets
Total assets	33,108,000	34,989,000
Operating Segments [Member] | High Power Group [Member]
Total assets
Total assets	36,786,000	33,306,000
Operating Segments [Member] | SL-MTI [Member]
Total assets
Total assets	23,842,000	22,752,000
Unallocated Corporate [Member]
Total assets
Total assets	$ 31,806,000	$ 40,729,000