Note 13 - Postretirement Medical Benefits (Tables) - Postretirement Health Coverage [Member]

12 Months Ended

Dec. 31, 2017

Notes Tables

Schedule of Changes in Projected Benefit Obligations [Table Text Block]

(In thousands)	201 7			201 6
Change in Benefit Obligation
Obligation at beginning of year	$	16,555		$	16,204
Service cost		557			637
Interest cost		660			683
Curtailment gain recognized		(417	)		-
Actuarial loss (gain)		263			(660	)
Participant contributions		196			153
Benefit payments		(550	)		(462	)
Obligation at end of year	$	17,264		$	16,555

Schedule of Net Benefit Costs [Table Text Block]

(In thousands)	201 7			201 6
Service cost	$	557		$	637
Interest cost		660			683
Curtailment gain recognized		(417	)		-
Recognized prior service cost		75			50
Net periodic benefit cost	$	875		$	1,370
Major assumptions:
Discount rate used to determine net periodic benefit cost		4.12	%		4.34	%
Discount rate used to determine benefit obligation as of year end		3.58			4.12
Retiree participation rate (Plan 1)		100.00			100.00
Retiree participation rate (Plan 2)		72.00			72.00

Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block]

(In thousands)	1% Increase		1% Decrease
Effect on total of service and interest cost components of net periodic postretirement health care benefit cost	$	295	$	(247	)
Effect on accumulated postretirement benefit obligation		3,530		(2,733	)

Schedule of Expected Benefit Payments [Table Text Block]

(In thousands)	Postretirement Medical Benefits
201 8	$	459
201 9		477
20 20		508
20 21		551
20 22		592
202 3-2027		3,439
Total	$	6,026

Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]

(In thousands)	201 7		201 6
Unrecognized net actuarial loss (gain)	$	169	$	(93	)
Unrecognized prior service cost		-		75
Total	$	169	$	(18	)