Note 10 - Concentration of Credit Risk (Details Textual) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Cash, Uninsured Amount	$ 18,925,000	$ 10,052,000

The amount of cash as of the balance sheet date that is not insured by the Federal Deposit Insurance Corporation.

No definition available.

Name:	us-gaap_CashUninsuredAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant