Note 2 - Income Tax Expense - Summary of Tax Years Subject to Examination in Most Significant Tax Jurisdictions (Details)	6 Months Ended
Jun. 30, 2020
Domestic Tax Authority [Member]
Income tax year under examination	2016 2017 2018 2019 2020
Foreign Tax Authority [Member]
Income tax year under examination	2013 2014 2015 2016 2017 2018 2019 2020

Tax year that remains open to examination under enacted tax laws, in CCYY format.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319

Name:	us-gaap_OpenTaxYear
Namespace Prefix:	us-gaap_
Data Type:	us-types:gYearListItemType
Balance Type:	na
Period Type:	duration