Note 10 - Accounting for Share-based Payment Arrangement Compensation (Details Textual) - USD ($)	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Stock or Unit Option Plan Expense	$ 321,000	$ 149,000

The noncash expense that accounts for the value of stock or unit options distributed to employees as compensation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

Name:	us-gaap_StockOptionPlanExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration