Note 8 - Retirement Plans - Matching Contributions (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Matching contributions to the Capital Accumulation Plan (in shares)	1,224	2,571	1,898
Matching contributions to the Capital Accumulation Plan	$ 15	$ 29	$ 26

Value of shares issued during the period to an employee benefit plan, such as a defined contribution or defined benefit plan.

No definition available.

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