Note 13 - Postretirement Medical Benefits (Details Textual) - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Number of Postretirement Medical and Dental Plan Participants | 37 | |
| Defined Benefit Plan, Contributions by Employer | $ 309 | $ 289 |
| Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year | $ 416 | |
| Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year | 6.50% | |
| Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Year Two | 6.00% | |
| Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Year Three | 5.50% | |
| Plan 2 [Member] | ||
| Employee Service Requirement | 20 years | |
| Employee Age Requirement | 55 years | |
| Contributions Plan 2 | 50.00% | |
| Plan 1 [Member] | ||
| Company Contributions Plan 1 | 100.00% | |
| Medical [Member] | ||
| Defined Benefit Plan, Ultimate Health Care Cost Trend Rate | 4.75% | |
| Dental [Member] | ||
| Defined Benefit Plan, Ultimate Health Care Cost Trend Rate | 5.00% | |