Note 3 - Accumulated Other Comprehensive (Loss) Income - Changes in Accumulated Other Comprehensive (Loss) Income by Component (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Beginning balance			$ 193,353	$ 184,066
Net current-period other comprehensive (loss) income	$ (1,113)	$ 1,339	(5,216)	2,352
Ending balance	197,892	192,876	197,892	192,876
Adoption of Accounting Standards Update 2016-01
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Beginning balance	(7,668)	(2,409)	(3,510)	(3,363)
Other comprehensive (loss) income before reclassifications	(1,112)	1,329	(5,214)	2,277
Amounts reclassified from accumulated other comprehensive income		1		7
Net current-period other comprehensive (loss) income	(1,112)	1,330	(5,214)	2,284
Ending balance	(8,780)	(1,079)	(8,780)	(1,079)
Adoption of Accounting Standards Update 2016-01	(56)		(56)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Beginning balance	(57)	14	(56)	(45)
Other comprehensive (loss) income before reclassifications		8		17
Amounts reclassified from accumulated other comprehensive income	(1)	1	(2)	51
Net current-period other comprehensive (loss) income	(1)	9	(2)	68
Ending balance	(58)	23	(58)	23
Adoption of Accounting Standards Update 2016-01
AOCI Attributable to Parent [Member]
Beginning balance	(7,725)	(2,395)	(3,566)	(3,408)
Other comprehensive (loss) income before reclassifications	(1,112)	1,337	(5,214)	2,294
Amounts reclassified from accumulated other comprehensive income	(1)	2	(2)	58
Net current-period other comprehensive (loss) income	(1,113)	1,339	(5,216)	2,352
Ending balance	(8,838)	(1,056)	(8,838)	(1,056)
Adoption of Accounting Standards Update 2016-01	$ (56)		$ (56)