Note 4 - Securities - Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Securities held-to-maturity, amortized cost	$ 31,165	$ 30,886
Securities held-to-maturity, fair value	28,217	29,699
Securities held-to-maturity, gross unrealized gains		0
Securities held-to-maturity, gross unrealized losses	2,948	1,187
Securities available for sale, amortized cost	790,241	748,350
Securities available for sale, fair value	761,032	738,354
Securities available for sale, gross unrealized gains	705	2,587
Securities available for sale, gross unrealized losses	29,914	12,583
Corporate Debt Securities [Member]
Securities available for sale, amortized cost	120,000	110,000
Securities available for sale, fair value	109,757	102,767
Securities available for sale, gross unrealized gains
Securities available for sale, gross unrealized losses	10,243	7,233
US States and Political Subdivisions Debt Securities [Member]
Securities held-to-maturity, amortized cost	23,207	22,913
Securities held-to-maturity, fair value	20,996	21,889
Securities held-to-maturity, gross unrealized gains		0
Securities held-to-maturity, gross unrealized losses	2,211	1,024
Securities available for sale, amortized cost	100,018	101,680
Securities available for sale, fair value	100,546	103,199
Securities available for sale, gross unrealized gains	589	1,519
Securities available for sale, gross unrealized losses	61
Other Debt Obligations [Member]
Securities held-to-maturity, amortized cost	23,207	22,913
Securities held-to-maturity, fair value	20,996	21,889
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	2,211	1,024
Securities available for sale, fair value	232,913	228,704
Mutual Fund Debt Securities [Member]
Securities available for sale, amortized cost	11,405	11,575
Securities available for sale, fair value	11,405	11,575
Securities available for sale, gross unrealized gains
Securities available for sale, gross unrealized losses
FNMA [Member]
Securities held-to-maturity, amortized cost	7,958	7,973
Securities held-to-maturity, fair value	7,221	7,810
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	737	163
Securities available for sale, amortized cost	130,397	136,198
Securities available for sale, fair value	125,168	135,474
Securities available for sale, gross unrealized gains	47	330
Securities available for sale, gross unrealized losses	5,276	1,054
Collateralized Debt Obligations [Member]
Securities available for sale, amortized cost	10,000	10,000
Securities available for sale, fair value	10,000	10,053
Securities available for sale, gross unrealized gains		53
Securities available for sale, gross unrealized losses
Collateralized Mortgage Backed Securities [Member]
Securities held-to-maturity, amortized cost	7,958	7,973
Securities held-to-maturity, fair value	7,221	7,810
Securities held-to-maturity, gross unrealized gains
Securities held-to-maturity, gross unrealized losses	737	163
Securities available for sale, amortized cost	547,613	513,985
Securities available for sale, fair value	528,119	509,650
Securities available for sale, gross unrealized gains	116	1,015
Securities available for sale, gross unrealized losses	19,610	5,350
Other Securities [Member]
Securities available for sale, amortized cost	1,205	1,110
Securities available for sale, fair value	1,205	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	242,628	234,365
Securities available for sale, fair value	232,913	228,704
Securities available for sale, gross unrealized gains	589	1,572
Securities available for sale, gross unrealized losses	10,304	7,233
REMIC and CMO [Member]
Securities available for sale, amortized cost	372,472	328,668
Securities available for sale, fair value	360,119	325,302
Securities available for sale, gross unrealized gains	17	595
Securities available for sale, gross unrealized losses	12,370	3,961
GNMA [Member]
Securities available for sale, amortized cost	805	1,016
Securities available for sale, fair value	848	1,088
Securities available for sale, gross unrealized gains	43	72
Securities available for sale, gross unrealized losses
FHLMC [Member]
Securities available for sale, amortized cost	43,939	48,103
Securities available for sale, fair value	41,984	47,786
Securities available for sale, gross unrealized gains	9	18
Securities available for sale, gross unrealized losses	$ 1,964	$ 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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