Note 10 - Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Loss) by Component, Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Beginning balance			$ 59,091	$ 54,073
Net of tax	$ (444)	$ 153	(1,695)	525
Ending Balance	59,610	59,753	59,610	59,753
Previously Reported [Member]
Beginning balance			59,091
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Beginning balance	(2,117)	(307)		(679)
Other comprehensive income before reclassification	(447)	153	(1,722)	421
Amounts reclassified from accumulated other comprehensive income (loss)	3		27	104
Net of tax	(444)	153	(1,695)	525
Cumulative effect of adoption of ASU 2016-01			(187)
Ending Balance	(2,561)	(154)	(2,561)	(154)
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Previously Reported [Member]
Beginning balance			(679)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Beginning balance	(4,839)	(3,812)		(3,812)
Other comprehensive income before reclassification
Amounts reclassified from accumulated other comprehensive income (loss)
Net of tax
Cumulative effect of adoption of ASU 2016-01
Ending Balance	(4,839)	(3,812)	(4,839)	(3,812)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] | Previously Reported [Member]
Beginning balance			(4,839)
AOCI Attributable to Parent [Member]
Beginning balance	(6,956)	(4,119)	(5,705)	(4,491)
Other comprehensive income before reclassification	(447)	153	(1,722)	421
Amounts reclassified from accumulated other comprehensive income (loss)	3		27	104
Net of tax	(444)	153	(1,695)	525
Cumulative effect of adoption of ASU 2016-01			(187)
Ending Balance	$ (7,400)	$ (3,966)	(7,400)	$ (3,966)
AOCI Attributable to Parent [Member] | Previously Reported [Member]
Beginning balance			$ (5,518)