Note 13 - Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Balance			$ 532,608	$ 513,853
Total other comprehensive income (loss), net of tax	$ (1,542)	$ (88)	(3,269)	1,698
Balance	541,756	539,609	541,756	539,609
Reclassification of the Income Tax Effects of the Tax Cuts and Jobs Act from Accumulated Other Comprehensive Income (Loss) to Retained Earnings			2,073
Impact of adoption of Accounting Standard Update 2016-01
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Balance	(16,501)	(2,110)	(5,522)	(3,859)
Other comprehensive income before reclassifications, net of tax	(3,505)	(333)	(13,159)	1,416
Amounts reclassified from accumulated other comprehensive income, net of tax		108		108
Total other comprehensive income (loss), net of tax	(3,505)	(225)	(13,159)	1,524
Balance	(20,006)	(2,335)	(20,006)	(2,335)
Reclassification of the Income Tax Effects of the Tax Cuts and Jobs Act from Accumulated Other Comprehensive Income (Loss) to Retained Earnings			(1,325)
Impact of adoption of Accounting Standard Update 2016-01
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Balance	8,027	(124)	231
Other comprehensive income before reclassifications, net of tax	1,950	56	9,455	(68)
Amounts reclassified from accumulated other comprehensive income, net of tax	(80)		161
Total other comprehensive income (loss), net of tax	1,870	56	9,616	(68)
Balance	9,897	(68)	9,897	(68)
Reclassification of the Income Tax Effects of the Tax Cuts and Jobs Act from Accumulated Other Comprehensive Income (Loss) to Retained Earnings			50
Impact of adoption of Accounting Standard Update 2016-01
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance	(4,325)	(4,342)	(3,695)	(4,503)
Other comprehensive income before reclassifications, net of tax
Amounts reclassified from accumulated other comprehensive income, net of tax	84	81	252	242
Total other comprehensive income (loss), net of tax	84	81	252	242
Balance	(4,241)	(4,261)	(4,241)	(4,261)
Reclassification of the Income Tax Effects of the Tax Cuts and Jobs Act from Accumulated Other Comprehensive Income (Loss) to Retained Earnings			(798)
Impact of adoption of Accounting Standard Update 2016-01
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Balance	792
Other comprehensive income before reclassifications, net of tax	9		22
Amounts reclassified from accumulated other comprehensive income, net of tax
Total other comprehensive income (loss), net of tax	9		22
Balance	801		801
Reclassification of the Income Tax Effects of the Tax Cuts and Jobs Act from Accumulated Other Comprehensive Income (Loss) to Retained Earnings
Impact of adoption of Accounting Standard Update 2016-01			779
AOCI Attributable to Parent [Member]
Balance	(12,007)	(6,576)	(8,986)	(8,362)
Other comprehensive income before reclassifications, net of tax	(1,546)	(277)	(3,682)	1,348
Amounts reclassified from accumulated other comprehensive income, net of tax	4	189	413	350
Total other comprehensive income (loss), net of tax	(1,542)	(88)	(3,269)	1,698
Balance	$ (13,549)	$ (6,664)	(13,549)	$ (6,664)
Reclassification of the Income Tax Effects of the Tax Cuts and Jobs Act from Accumulated Other Comprehensive Income (Loss) to Retained Earnings			(2,073)
Impact of adoption of Accounting Standard Update 2016-01			$ 779