Note 4 - Securities - Amortized Cost and Fair Value of Securities (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Securities held-to-maturity, amortized cost	$ 60,186,000	$ 32,018,000
Securities held-to-maturity, fair value	62,169,000	29,874,000
Securities held-to-maturity, gross unrealized gains	1,983,000	0
Securities held-to-maturity, gross unrealized losses	0	2,144,000
Securities available for sale, amortized cost, total other securities	814,176,000	845,332,000
Securities available for sale, fair value	808,653,000	822,655,000
Securities available for sale, gross unrealized gains	5,114,000	1,454,000
Securities available for sale, gross unrealized losses	10,637,000	24,131,000
Corporate Debt Securities [Member]
Securities available for sale, amortized cost, total other securities	130,000,000	130,000,000
Securities available for sale, fair value	122,036,000	118,535,000
Securities available for sale, gross unrealized gains	0	0
Securities available for sale, gross unrealized losses	7,964,000	11,465,000
US States and Political Subdivisions Debt Securities [Member]
Securities held-to-maturity, amortized cost	52,242,000	24,065,000
Securities held-to-maturity, fair value	54,131,000	22,508,000
Securities held-to-maturity, gross unrealized gains	1,889,000	0
Securities held-to-maturity, gross unrealized losses	0	1,557,000
Securities available for sale, amortized cost, total other securities	18,908,000	46,231,000
Securities available for sale, fair value	19,141,000	46,574,000
Securities available for sale, gross unrealized gains	233,000	343,000
Securities available for sale, gross unrealized losses	0	0
Other Debt Obligations [Member]
Securities held-to-maturity, amortized cost	52,242,000	24,065,000
Securities held-to-maturity, fair value	54,131,000	22,508,000
Securities held-to-maturity, gross unrealized gains	1,889,000	0
Securities held-to-maturity, gross unrealized losses	0	1,557,000
Securities available for sale, fair value	254,172,000	264,702,000
Mutual Fund Debt Securities [Member]
Securities available for sale, amortized cost, total other securities	12,042,000	11,586,000
Securities available for sale, fair value	12,042,000	11,586,000
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	7,944,000	7,953,000
Securities held-to-maturity, fair value	8,038,000	7,366,000
Securities held-to-maturity, gross unrealized gains	94,000	0
Securities held-to-maturity, gross unrealized losses	0	587,000
Securities available for sale, amortized cost, total other securities	96,445,000	94,069,000
Securities available for sale, fair value	96,445,000	91,693,000
Securities available for sale, gross unrealized gains	572,000	72,000
Securities available for sale, gross unrealized losses	572,000	2,448,000
Collateralized Debt Obligations [Member]
Securities available for sale, amortized cost, total other securities	100,324,000	88,396,000
Securities available for sale, fair value	99,650,000	86,751,000
Securities available for sale, gross unrealized gains	60,000	0
Securities available for sale, gross unrealized losses	734,000	1,645,000
Collateralized Mortgage Backed Securities [Member]
Securities held-to-maturity, amortized cost	7,944,000	7,953,000
Securities held-to-maturity, fair value	8,038,000	7,366,000
Securities held-to-maturity, gross unrealized gains	94,000	0
Securities held-to-maturity, gross unrealized losses	0	587,000
Securities available for sale, amortized cost, total other securities	551,599,000	567,863,000
Securities available for sale, fair value	554,481,000	557,953,000
Securities available for sale, gross unrealized gains	4,821,000	1,111,000
Securities available for sale, gross unrealized losses	1,939,000	11,021,000
Other Securities [Member]
Securities available for sale, amortized cost, total other securities	1,303,000	1,256,000
Securities available for sale, fair value	1,303,000	1,256,000
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	262,577,000	277,469,000
Securities available for sale, fair value	254,172,000	264,702,000
Securities available for sale, gross unrealized gains	293,000	343,000
Securities available for sale, gross unrealized losses	8,698,000	13,110,000
REMIC and CMO [Member]
Securities available for sale, amortized cost, total other securities	370,689,000	382,632,000
Securities available for sale, fair value	372,761,000	376,340,000
Securities available for sale, gross unrealized gains	3,181,000	885,000
Securities available for sale, gross unrealized losses	1,109,000	7,177,000
GNMA [Member]
Securities available for sale, amortized cost, total other securities	734,000	785,000
Securities available for sale, fair value	790,000	826,000
Securities available for sale, gross unrealized gains	56,000	41,000
Securities available for sale, gross unrealized losses	0	0
FHLMC [Member]
Securities available for sale, amortized cost, total other securities	83,731,000	90,377,000
Securities available for sale, fair value	84,485,000	89,094,000
Securities available for sale, gross unrealized gains	1,012,000	113,000
Securities available for sale, gross unrealized losses	$ 258,000	$ 1,396,000

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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