Note 3 - Accumulated Other Comprehensive Income - Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Beginning balance			$ 184,066	$ 175,698
Net current-period other comprehensive income (loss)	$ 126	$ (3,976)	2,478	339
Ending balance	197,648	188,724	197,648	188,724
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Beginning balance	(1,079)	7,516	(3,363)	3,219
Other comprehensive income (loss) before reclassifications	120	(1,531)	2,397	2,905
Amounts reclassified from accumulated other comprehensive income	(2)	(2,454)	5	(2,593)
Net current-period other comprehensive income (loss)	118	(3,985)	2,402	312
Ending balance	(961)	3,531	(961)	3,531
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Beginning balance	23	(419)	(45)	(437)
Other comprehensive income (loss) before reclassifications	7	0	25	0
Amounts reclassified from accumulated other comprehensive income	1	9	51	27
Net current-period other comprehensive income (loss)	8	9	76	27
Ending balance	31	(410)	31	(410)
AOCI Attributable to Parent [Member]
Beginning balance	(1,056)	7,097	(3,408)	2,782
Other comprehensive income (loss) before reclassifications	127	(1,531)	2,422	2,905
Amounts reclassified from accumulated other comprehensive income	(1)	(2,445)	56	(2,566)
Net current-period other comprehensive income (loss)	126	(3,976)	2,478	339
Ending balance	$ (930)	$ 3,121	$ (930)	$ 3,121