Note 4 - Securities - Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Securities held-to-maturity, amortized cost	$ 30,481	$ 32,018
Securities held-to-maturity, fair value	30,002	29,874
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	479	2,144
Securities available for sale, amortized cost	860,558	845,332
Securities available for sale, fair value	846,024	822,655
Securities available for sale, gross unrealized gains	2,777	1,454
Securities available for sale, gross unrealized losses	17,311	24,131
Corporate Debt Securities [Member]
Securities available for sale, amortized cost	130,000	130,000
Securities available for sale, fair value	121,382	118,535
Securities available for sale, gross unrealized gains
Securities available for sale, gross unrealized losses	8,618	11,465
US States and Political Subdivisions Debt Securities [Member]
Securities held-to-maturity, amortized cost	22,532	24,065
Securities held-to-maturity, fair value	22,276	22,508
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	256	1,557
Securities available for sale, amortized cost	32,772	46,231
Securities available for sale, fair value	33,061	46,574
Securities available for sale, gross unrealized gains	289	343
Securities available for sale, gross unrealized losses
Other Debt Obligations [Member]
Securities held-to-maturity, amortized cost	22,532	24,065
Securities held-to-maturity, fair value	22,276	22,508
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	256	1,557
Securities available for sale, fair value	266,839	264,702
Mutual Fund Debt Securities [Member]
Securities available for sale, amortized cost	11,802	11,586
Securities available for sale, fair value	11,802	11,586
Securities available for sale, gross unrealized gains
Securities available for sale, gross unrealized losses
FNMA [Member]
Securities held-to-maturity, amortized cost	7,949	7,953
Securities held-to-maturity, fair value	7,726	7,366
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	223	587
Securities available for sale, amortized cost	95,360	94,069
Securities available for sale, fair value	94,197	91,693
Securities available for sale, gross unrealized gains	302	72
Securities available for sale, gross unrealized losses	1,465	2,448
Collateralized Debt Obligations [Member]
Securities available for sale, amortized cost	100,311	88,396
Securities available for sale, fair value	99,305	86,751
Securities available for sale, gross unrealized gains	10
Securities available for sale, gross unrealized losses	1,016	1,645
Collateralized Mortgage Backed Securities [Member]
Securities held-to-maturity, amortized cost	7,949	7,953
Securities held-to-maturity, fair value	7,726	7,366
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	223	587
Securities available for sale, amortized cost	584,384	567,863
Securities available for sale, fair value	579,185	557,953
Securities available for sale, gross unrealized gains	2,478	1,111
Securities available for sale, gross unrealized losses	7,677	11,021
Other Securities [Member]
Securities available for sale, amortized cost	1,289	1,256
Securities available for sale, fair value	1,289	1,256
Securities available for sale, gross unrealized gains
Securities available for sale, gross unrealized losses
Available for Sale Securities Excluding Mortgage Backed Securities [Member]
Securities available for sale, amortized cost	276,174	277,469
Securities available for sale, fair value	266,839	264,702
Securities available for sale, gross unrealized gains	299	343
Securities available for sale, gross unrealized losses	9,634	13,110
REMIC and CMO [Member]
Securities available for sale, amortized cost	400,522	382,632
Securities available for sale, fair value	396,890	376,340
Securities available for sale, gross unrealized gains	1,719	885
Securities available for sale, gross unrealized losses	5,351	7,177
GNMA [Member]
Securities available for sale, amortized cost	766	785
Securities available for sale, fair value	810	826
Securities available for sale, gross unrealized gains	44	41
Securities available for sale, gross unrealized losses
FHLMC [Member]
Securities available for sale, amortized cost	87,736	90,377
Securities available for sale, fair value	87,288	89,094
Securities available for sale, gross unrealized gains	413	113
Securities available for sale, gross unrealized losses	$ 861	$ 1,396

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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