Note 10 - Commitments and Contingencies (Details Textual) € in Millions	1 Months Ended
Oct. 31, 2016 EUR (€)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Loss Contingency Accrual, Ending Balance		$ 0	$ 0
Solaria Energia y Medio Ambiente S.A. [Member] \| Damages from Product Defects [Member]
Loss Contingency Accrual, Ending Balance		0	0
Loss Contingency, Damages Sought, Value \| €	€ 3.3
Phase II Environmental Site Assessment [Member]
Accrual for Environmental Loss Contingencies, Ending Balance		$ 57,000	$ 57,000

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

Name:	us-gaap_LossContingencyDamagesSoughtValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration