Note 3 - Comprehensive Income - Amounts Reclassified Out of Each Component of OCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Unrealized gains and losses on available-for-sale Securities	$ (5)	$ (584)	$ (257)	$ (1,089)
Income tax provision	1,262	1,451	3,620	3,847
Net income	(3,936)	(4,087)	(11,491)	(11,531)
Total before tax	(5,198)	(5,538)	(15,111)	(15,378)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Net income	(8)	(383)	(180)	(718)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Unrealized gains and losses on available-for-sale Securities	(5)	(584)	(257)	(1,089)
Income tax provision	1	204	89	381
Net income	(4)	(380)	(168)	(708)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Income tax provision	2	2	6	5
Net income	(4)	(3)	(12)	(10)
Prior service cost	(8)	(8)	(23)	(23)
Actuarial loss	2	3	5	8
Total before tax	$ (6)	$ (5)	$ (18)	$ (15)