Note 4 - Securities - Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Securities held-to-maturity, amortized cost	$ 60,040	$ 32,018
Securities held-to-maturity, fair value	63,870	29,874
Securities held-to-maturity, gross unrealized gains	3,830	0
Securities held-to-maturity, gross unrealized losses	0	2,144
Securities available for sale, amortized cost, total other securities	831,687	845,332
Securities available for sale, fair value	825,475	822,655
Securities available for sale, gross unrealized gains	5,831	1,454
Securities available for sale, gross unrealized losses	12,043	24,131
Corporate Debt Securities [Member]
Securities available for sale, amortized cost, total other securities	130,000	130,000
Securities available for sale, fair value	120,543	118,535
Securities available for sale, gross unrealized gains	0	0
Securities available for sale, gross unrealized losses	9,457	11,465
US States and Political Subdivisions Debt Securities [Member]
Securities held-to-maturity, amortized cost	52,101	24,065
Securities held-to-maturity, fair value	55,498	22,508
Securities held-to-maturity, gross unrealized gains	3,397	0
Securities held-to-maturity, gross unrealized losses	0	1,557
Securities available for sale, amortized cost, total other securities	12,849	46,231
Securities available for sale, fair value	13,017	46,574
Securities available for sale, gross unrealized gains	168	343
Securities available for sale, gross unrealized losses	0	0
Other Debt Obligations [Member]
Securities held-to-maturity, amortized cost	52,101	24,065
Securities held-to-maturity, fair value	55,498	22,508
Securities held-to-maturity, gross unrealized gains	3,397	0
Securities held-to-maturity, gross unrealized losses	0	1,557
Securities available for sale, fair value	246,465	264,702
Mutual Fund Debt Securities [Member]
Securities available for sale, amortized cost, total other securities	12,206	11,586
Securities available for sale, fair value	12,206	11,586
Securities available for sale, gross unrealized gains	0	0
Securities available for sale, gross unrealized losses	0	0
FNMA [Member]
Securities held-to-maturity, amortized cost	7,939	7,953
Securities held-to-maturity, fair value	8,372	7,366
Securities held-to-maturity, gross unrealized gains	433	0
Securities held-to-maturity, gross unrealized losses	0	587
Securities available for sale, amortized cost, total other securities	106,773	94,069
Securities available for sale, fair value	107,383	91,693
Securities available for sale, gross unrealized gains	998	72
Securities available for sale, gross unrealized losses	388	2,448
Collateralized Debt Obligations [Member]
Securities available for sale, amortized cost, total other securities	100,336	88,396
Securities available for sale, fair value	99,381	86,751
Securities available for sale, gross unrealized gains	5	0
Securities available for sale, gross unrealized losses	960	1,645
Collateralized Mortgage Backed Securities [Member]
Securities held-to-maturity, amortized cost	7,939	7,953
Securities held-to-maturity, fair value	8,372	7,366
Securities held-to-maturity, gross unrealized gains	433	0
Securities held-to-maturity, gross unrealized losses	0	587
Securities available for sale, amortized cost, total other securities	574,978	567,863
Securities available for sale, fair value	579,010	557,953
Securities available for sale, gross unrealized gains	5,658	1,111
Securities available for sale, gross unrealized losses	1,626	11,021
Other Securities [Member]
Securities available for sale, amortized cost, total other securities	1,318	1,256
Securities available for sale, fair value	1,318	1,256
Securities available for sale, gross unrealized gains	0	0
Securities available for sale, gross unrealized losses	0	0
Available for Sale Securities Excluding Mortgage Backed Securities [Member]
Securities available for sale, amortized cost, total other securities	256,709	277,469
Securities available for sale, fair value	246,465	264,702
Securities available for sale, gross unrealized gains	173	343
Securities available for sale, gross unrealized losses	10,417	13,110
REMIC and CMO [Member]
Securities available for sale, amortized cost, total other securities	390,044	382,632
Securities available for sale, fair value	392,525	376,340
Securities available for sale, gross unrealized gains	3,604	885
Securities available for sale, gross unrealized losses	1,123	7,177
GNMA [Member]
Securities available for sale, amortized cost, total other securities	706	785
Securities available for sale, fair value	764	826
Securities available for sale, gross unrealized gains	58	41
Securities available for sale, gross unrealized losses	0	0
FHLMC [Member]
Securities available for sale, amortized cost, total other securities	77,455	90,377
Securities available for sale, fair value	78,338	89,094
Securities available for sale, gross unrealized gains	998	113
Securities available for sale, gross unrealized losses	$ 115	$ 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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