Note 4 -Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2017 USD ($) security	Dec. 31, 2016 USD ($) security
Schedule Of Available For Sale Securities [Line Items]
No. of securities | security	275	306
Securities in an unrealized loss position less than 12 months, fair value	$ 109,879	$ 288,833
Securities in an unrealized loss position less than 12 months, unrealized losses	(1,555)	(6,351)
Securities in an unrealized loss position 12 months or longer, fair value	190,771	18,266
Securities in an unrealized loss position 12 months or longer, unrealized losses	(5,611)	(1,528)
Securities in an unrealized loss position, fair value	300,650	307,099
Securities in an unrealized loss position, unrealized losses	$ (7,166)	$ (7,879)
US Government Agencies Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of securities | security	53	55
Securities in an unrealized loss position less than 12 months, fair value	$ 10,828	$ 72,626
Securities in an unrealized loss position less than 12 months, unrealized losses	(155)	(2,118)
Securities in an unrealized loss position 12 months or longer, fair value	59,696
Securities in an unrealized loss position 12 months or longer, unrealized losses	(1,793)
Securities in an unrealized loss position, fair value	70,524	72,626
Securities in an unrealized loss position, unrealized losses	$ (1,948)	$ (2,118)
US States and Political Subdivisions Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of securities | security	37	70
Securities in an unrealized loss position less than 12 months, fair value	$ 10,577	$ 29,280
Securities in an unrealized loss position less than 12 months, unrealized losses	(49)	(398)
Securities in an unrealized loss position 12 months or longer, fair value	4,446
Securities in an unrealized loss position 12 months or longer, unrealized losses	(64)
Securities in an unrealized loss position, fair value	15,023	29,280
Securities in an unrealized loss position, unrealized losses	$ (113)	$ (398)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of securities | security	99	88
Securities in an unrealized loss position less than 12 months, fair value	$ 61,069	$ 123,087
Securities in an unrealized loss position less than 12 months, unrealized losses	(705)	(2,241)
Securities in an unrealized loss position 12 months or longer, fair value	72,318
Securities in an unrealized loss position 12 months or longer, unrealized losses	(1,696)
Securities in an unrealized loss position, fair value	133,387	123,087
Securities in an unrealized loss position, unrealized losses	$ (2,401)	$ (2,241)
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of securities | security	70	68
Securities in an unrealized loss position less than 12 months, fair value	$ 21,660	$ 56,853
Securities in an unrealized loss position less than 12 months, unrealized losses	(349)	(1,269)
Securities in an unrealized loss position 12 months or longer, fair value	52,833	15,426
Securities in an unrealized loss position 12 months or longer, unrealized losses	(1,943)	(577)
Securities in an unrealized loss position, fair value	74,493	72,279
Securities in an unrealized loss position, unrealized losses	$ (2,292)	$ (1,846)
Collateralized Debt Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of securities | security	1	5
Securities in an unrealized loss position less than 12 months, fair value	$ 0	$ 0
Securities in an unrealized loss position less than 12 months, unrealized losses	0	0
Securities in an unrealized loss position 12 months or longer, fair value	215	1,952
Securities in an unrealized loss position 12 months or longer, unrealized losses	(26)	(891)
Securities in an unrealized loss position, fair value	215	1,952
Securities in an unrealized loss position, unrealized losses	$ (26)	$ (891)
Corporate Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of securities | security	4	4
Securities in an unrealized loss position less than 12 months, fair value	$ 3,018	$ 4,002
Securities in an unrealized loss position less than 12 months, unrealized losses	(20)	(57)
Securities in an unrealized loss position 12 months or longer, fair value	988
Securities in an unrealized loss position 12 months or longer, unrealized losses	(17)
Securities in an unrealized loss position, fair value	4,006	4,002
Securities in an unrealized loss position, unrealized losses	$ (37)	$ (57)
Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of securities | security	11	16
Securities in an unrealized loss position less than 12 months, fair value	$ 2,727	$ 2,985
Securities in an unrealized loss position less than 12 months, unrealized losses	(277)	(268)
Securities in an unrealized loss position 12 months or longer, fair value	275	888
Securities in an unrealized loss position 12 months or longer, unrealized losses	(72)	(60)
Securities in an unrealized loss position, fair value	3,002	3,873
Securities in an unrealized loss position, unrealized losses	$ (349)	$ (328)