Note 15 - Commitments and Contingencies (Details Textual) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Letters of Credit Issued and Available Amount	$ 1.9
Line of Credit Facility, Expiration Period	2 years 210 days

Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_LineOfCreditFacilityExpirationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration