Note 13 - Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive 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
Balance			$ 532,608	$ 513,853
Total other comprehensive income (loss), net of tax	$ (832)	$ 558	(1,727)	1,786
Balance	538,044	534,091	538,044	534,091
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
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Balance	(13,487)	(2,711)	(5,522)	(3,859)
Other comprehensive income before reclassifications, net of tax	(3,014)	601	(9,654)	1,749
Amounts reclassified from accumulated other comprehensive income, net of tax
Total other comprehensive income (loss), net of tax	(3,014)	601	(9,654)	1,749
Balance	(16,501)	(2,110)	(16,501)	(2,110)
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	5,942		231
Other comprehensive income before reclassifications, net of tax	1,898	(124)	7,505	(124)
Amounts reclassified from accumulated other comprehensive income, net of tax	187		241
Total other comprehensive income (loss), net of tax	2,085	(124)	7,746	(124)
Balance	8,027	(124)	8,027	(124)
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	(4,409)	(4,423)	(3,695)	(4,503)
Other comprehensive income before reclassifications, net of tax
Amounts reclassified from accumulated other comprehensive income, net of tax	84	81	168	161
Total other comprehensive income (loss), net of tax	84	81	168	161
Balance	(4,325)	(4,342)	(4,325)	(4,342)
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	779
Other comprehensive income before reclassifications, net of tax	13		13
Amounts reclassified from accumulated other comprehensive income, net of tax
Total other comprehensive income (loss), net of tax	13		13
Balance	792		792
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	(11,175)	(7,134)	(8,986)	(8,362)
Other comprehensive income before reclassifications, net of tax	(1,103)	477	(2,136)	1,625
Amounts reclassified from accumulated other comprehensive income, net of tax	271	81	409	161
Total other comprehensive income (loss), net of tax	(832)	558	(1,727)	1,786
Balance	$ (12,007)	$ (6,576)	(12,007)	$ (6,576)
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