Note 2 - INVESTMENT SECURITIES - Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Securities held to maturity:
Securities held to maturity, due in one year or less, amortized cost	$ 3,592
Securities held to maturity, due in one year or less, fair value	3,611
Securities held to maturity, due after one year through five years, amortized cost	32,784
Securities held to maturity, due after one year through five years, fair value	33,424
Securities held to maturity, due after five years, amortized cost	416,750
Securities held to maturity, due after five years, fair value	454,312
Securities held to maturity, amortized cost	453,126
Securities held to maturity, fair value	491,347	$ 521,277
Securities available for sale:
Securities available for sale, due in one year or less, amortized cost	2,152
Securities available for sale, Due in one year or less, fair value	2,182
Securities available for sale, due after one year through five years, amortized cost	12,888
Securities available for sale, Due after one year through five years, fair value	13,175
Securities available for sale, due after five years, amortized cost	171,836
Securities available for sale, due after five years, fair value	173,649
Securities available for sale, single maturity, amortized cost	186,876
Securities available for sale, single maturity, fair value	189,006
Securities available for sale, amortized cost	340,726	350,060
Securities available for sale, fair value	346,873	361,966
Securities available for sale, callable, amortized cost	340,726
Securities available for sale, callable, fair value	346,873
Callable Securities [Member]
Securities available for sale:
Securities available for sale, amortized cost	166,111
Securities available for sale, fair value	167,868
Municipal securities
Securities held to maturity:
Securities held to maturity, fair value	490,297	520,227
Securities available for sale:
Securities available for sale, amortized cost	160,703	147,241
Securities available for sale, fair value	162,573	152,408
Municipal securities | Callable Securities [Member]
Securities held to maturity:
Securities held to maturity, callable, amortized cost	246,515
Securities held to maturity, callable, fair value	255,969
Securities available for sale:
Securities available for sale, callable, amortized cost	154,432
Securities available for sale, callable, fair value	156,016
Asset-backed securities
Securities available for sale:
Securities available for sale, amortized cost	38,620	39,663
Securities available for sale, fair value	39,815	40,683
Securities available for sale, callable, amortized cost	38,620
Securities available for sale, callable, fair value	39,815
Residential mortgage-backed and related securities
Securities available for sale:
Securities available for sale, amortized cost	115,230	127,670
Securities available for sale, fair value	118,052	132,842
Securities available for sale, callable, amortized cost	115,230
Securities available for sale, callable, fair value	118,052
Other Securities
Securities held to maturity:
Securities held to maturity, fair value	1,050	1,050
Securities available for sale:
Securities available for sale, amortized cost	11,679	20,550
Securities available for sale, fair value	11,852	$ 20,697
Other Securities | Callable Securities [Member]
Securities available for sale:
Securities available for sale, callable, amortized cost	11,679
Securities available for sale, callable, fair value	$ 11,852