Note 11 - Business Segment Information (Detail) (USD $)	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Number of Operating Segments	2
Entity Wide Revenue, Major Customer, Number	1	3
Power And Energy Group [Member]
Proceeds from Customers for Progress Payments (in Dollars)	2,664,000
Utility-Scale Energy Storage System [Member]
Segment Reporting Information, Revenue for Reportable Segment (in Dollars)	1,291,000
Minimum [Member]
Entity-Wide Revenue, Major Customer, Percentage	10.00%	10.00%

Amount of total revenue for the reportable segments, including revenue from external customers, transactions with other operating segments of the same entity, and (gross) interest revenue. All considered to be "operating revenue" for purposes of the taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 280

-SubTopic 10

-Section 50

-Paragraph 22

-Subparagraph (a),(b),(c)

-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8736-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 27

-Subparagraph a, b, c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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