Note 5 - Deferred Revenue - Summary of Deferred Service Contract Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Deferred service contract revenue	$ 10,719	$ 9,431
Add: Payments received	14,882	14,369
Less: Revenue recognized	(13,746)	(13,081)
Deferred service contract revenue	$ 11,855	$ 10,719

Amount of deferred revenue recognized for transactions arising during the current reporting period. Deferred revenue is a liability as of the balance sheet date related to a revenue producing activity for which revenue has not yet been recognized. Generally, an Entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

No definition available.

Name:	us-gaap_DeferredRevenueAdditions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration