Note 2 - Summary of Significant Accounting Policies - Practical expedients (Details)	9 Months Ended
Sep. 30, 2019
Accounting Policies [Abstract]
Lease, Practical Expedient, Lessor Single Lease Component [true false]	true
Lease, Practical Expedients, Package [true false]	true

Indicates (true false) whether practical expedients are elected for not reassessing whether any expired or existing contract is or contains lease, lease classification for expired or existing lease, and initial direct cost for any existing lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 10
-Section 65
-Paragraph 1
-Subparagraph (j)
-URI http://asc.fasb.org/extlink&oid=119364159&loc=SL77916155-209984

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 10
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=119364159&loc=SL77916155-209984

Name:	us-gaap_LeasePracticalExpedientsPackage
Namespace Prefix:	us-gaap_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration