Note 4 - Securities - Securities Available-for-sale and Held-to-maturity by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Securities held-to-maturity, amortized cost, due in one year or less	$ 1,180
Securities held-to-maturity, fair value, due in one year or less	1,180
Securities held-to-maturity, amortized cost, due after ten years	50,921
Securities held-to-maturity, fair value, due after ten years	54,318
Securities held-to-maturity, amortized cost	60,040	$ 32,018
Securities held-to-maturity, fair value	63,870	29,874
Securities available for sale, amortized cost, due after one year through five years	10,000
Securities available for sale, fair value, due after one year through five years	9,762
Securities available for sale, amortized cost, due after five years through ten years	137,913
Securities available for sale, fair value, due after five years through ten years	128,645
Securities available for sale, amortized cost, due after ten years	96,590
Securities available for sale, fair value, due after ten years	95,852
Securities available for sale, amortized cost, total other securities	831,687	845,332
Securities available for sale	825,475	822,655
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 available for sale	246,465	264,702
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 available for sale, amortized cost, total other securities	574,978	567,863
Securities available for sale	579,010	557,953
Total Other Securities [Member]
Securities available for sale, amortized cost, total other securities	244,503
Securities available for sale	234,259
Mutual Fund Debt Securities [Member]
Securities available for sale, amortized cost, total other securities	12,206	11,586
Securities available for sale	$ 12,206	$ 11,586

Amortized cost of 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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