Note 4 - Securities - Securities Available-for-sale and Held-to-maturity by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 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	51,062
Securities held-to-maturity, fair value, due after ten years	52,951
Securities held-to-maturity, amortized cost	60,186	$ 32,018
Securities held-to-maturity, fair value	62,169	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	9,683
Securities available for sale, amortized cost, due after five years through ten years	137,910
Securities available for sale, fair value, due after five years through ten years	130,259
Securities available for sale, amortized cost, due after ten years	102,625
Securities available for sale, fair value, due after ten years	102,188
Securities available for sale, amortized cost, total other securities	814,176	845,332
Securities available for sale	808,653	822,655
Other Debt Obligations [Member]
Securities held-to-maturity, amortized cost	52,242	24,065
Securities held-to-maturity, fair value	54,131	22,508
Securities available for sale	254,172	264,702
Collateralized Mortgage Backed Securities [Member]
Securities held-to-maturity, amortized cost	7,944	7,953
Securities held-to-maturity, fair value	8,038	7,366
Securities available for sale, amortized cost, total other securities	551,599	567,863
Securities available for sale	554,481	557,953
Total Other Securities [Member]
Securities available for sale, amortized cost, total other securities	250,535
Securities available for sale	242,130
Mutual Fund Debt Securities [Member]
Securities available for sale, amortized cost, total other securities	12,042	11,586
Securities available for sale	$ 12,042	$ 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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