Note 9 - Leases (Details Textual) - USD ($)	9 Months Ended
Sep. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Direct financing leases	$ 0
Net investment in sales-type leases	4,000,000	$ 3,000,000
Income recognized for sales-type lease arrangements	$ 0

Amount of lease income from variable lease payments, interest income from net investment on sales-type lease, and profit (loss) recognized at commencement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=77888421&loc=SL77919311-209978

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 50
-Paragraph 6A
-URI http://asc.fasb.org/extlink&oid=118952077&loc=SL77927221-108306

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=119202524&loc=SL77919372-209981

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