Note 8 - Fair Value of Financial Instruments - (Details Textual) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Recurring [Member]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	$ 0
Fair Value, Nonrecurring [Member]
Financial and Nonfinancial Liabilities, Fair Value Disclosure		$ 0

Fair value of financial and nonfinancial obligations.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

Name:	us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant