Note 7 - Segment and Geographic Information (Details) - Revenue by Product Family - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenue from External Customer [Line Items]
Product family	$ 81,416	$ 68,436	$ 154,954	$ 128,497
DC To DC Products [Member]
Revenue from External Customer [Line Items]
Product family	73,195	61,173	139,492	115,108
Lighting Control Products [Member]
Revenue from External Customer [Line Items]
Product family	$ 8,221	$ 7,263	$ 15,462	$ 13,389

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration