Segment Information - Goodwill and Other Intangible Assets, Net by Segment (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Goodwill and other intangible assets, net
Goodwill and other intangible assets, net	$ 16,813	$ 16,860
SLPE [Member]
Goodwill and other intangible assets, net
Goodwill and other intangible assets, net	4,528	4,530
High Power Group [Member]
Goodwill and other intangible assets, net
Goodwill and other intangible assets, net	9,842	9,839
SL-MTI [Member]
Goodwill and other intangible assets, net
Goodwill and other intangible assets, net	$ 2,443	$ 2,491