Note 1 - Basis of Presentation (Details Textual) - Reclassification from Accrued Expenses to Customer Deposits [Member]	6 Months Ended
Jun. 30, 2018 USD ($)
Year Ended December 31, 2017 [Member]
Prior Period Reclassification Adjustment	$ 297,000
Six Months Ended June 30, 2017 [Member]
Prior Period Reclassification Adjustment	$ 67,000

The amount of a reclassification adjustment made to prior period financial statement amounts.

No definition available.

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