Note 7 - Share-based Payments - Amounts of Compensation Expense Recognized Under Stock-based Payment Programs (Details) (Parentheticals)	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2016
Employee Stock Purchase Plan [Member]
Stock compensation expense, discount rate	15.00%	15.00%

Discount rate from fair value on purchase date that participants pay for shares.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration