Note 6 - Securities - Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Securities held-to-maturity, amortized cost	$ 32,018	$ 30,886
Securities held-to-maturity, fair value	29,874	29,699
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	2,144	1,187
Securities available for sale, amortized cost, total other securities	845,332	748,350
Securities available for sale, fair value	822,655	738,354
Securities available for sale, gross unrealized gains	1,454	2,587
Securities available for sale, gross unrealized losses	24,131	12,583
Corporate Debt Securities [Member]
Securities available for sale, amortized cost, total other securities	130,000	110,000
Securities available for sale, fair value	118,535	102,767
Securities available for sale, gross unrealized gains
Securities available for sale, gross unrealized losses	11,465	7,233
US States and Political Subdivisions Debt Securities [Member]
Securities held-to-maturity, amortized cost	24,065	22,913
Securities held-to-maturity, fair value	22,508	21,889
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	1,557	1,024
Securities available for sale, amortized cost, total other securities	46,231	101,680
Securities available for sale, fair value	46,574	103,199
Securities available for sale, gross unrealized gains	343	1,519
Securities available for sale, gross unrealized losses
Other Debt Obligations [Member]
Securities held-to-maturity, amortized cost	24,065	22,913
Securities held-to-maturity, fair value	22,508	21,889
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	1,557	1,024
Securities available for sale, fair value	264,702	228,704
Mutual Fund Debt Securities [Member]
Securities available for sale, amortized cost, total other securities	11,586	11,575
Securities available for sale, fair value	11,586	11,575
Securities available for sale, gross unrealized gains
Securities available for sale, gross unrealized losses
FNMA [Member]
Securities held-to-maturity, amortized cost	7,953	7,973
Securities held-to-maturity, fair value	7,366	7,810
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	587	163
Securities available for sale, amortized cost, total other securities	94,069	136,198
Securities available for sale, fair value	91,693	135,474
Securities available for sale, gross unrealized gains	72	330
Securities available for sale, gross unrealized losses	2,448	1,054
Collateralized Debt Obligations [Member]
Securities available for sale, amortized cost, total other securities	88,396	10,000
Securities available for sale, fair value	86,751	10,053
Securities available for sale, gross unrealized gains		53
Securities available for sale, gross unrealized losses	1,645
Collateralized Mortgage Backed Securities [Member]
Securities held-to-maturity, amortized cost	7,953	7,973
Securities held-to-maturity, fair value	7,366	7,810
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	587	163
Securities available for sale, amortized cost, total other securities	567,863	513,985
Securities available for sale, fair value	557,953	509,650
Securities available for sale, gross unrealized gains	1,111	1,015
Securities available for sale, gross unrealized losses	11,021	5,350
Other Securities [Member]
Securities available for sale, amortized cost, total other securities	1,256	1,110
Securities available for sale, fair value	1,256	1,110
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, total other securities	277,469	234,365
Securities available for sale, fair value	264,702	228,704
Securities available for sale, gross unrealized gains	343	1,572
Securities available for sale, gross unrealized losses	13,110	7,233
REMIC and CMO [Member]
Securities available for sale, amortized cost, total other securities	382,632	328,668
Securities available for sale, fair value	376,340	325,302
Securities available for sale, gross unrealized gains	885	595
Securities available for sale, gross unrealized losses	7,177	3,961
GNMA [Member]
Securities available for sale, amortized cost, total other securities	785	1,016
Securities available for sale, fair value	826	1,088
Securities available for sale, gross unrealized gains	41	72
Securities available for sale, gross unrealized losses
FHLMC [Member]
Securities available for sale, amortized cost, total other securities	90,377	48,103
Securities available for sale, fair value	89,094	47,786
Securities available for sale, gross unrealized gains	113	18
Securities available for sale, gross unrealized losses	$ 1,396	$ 335

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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