Note 14 - Stockholders' Equity and Regulatory Requirements - Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations (Details) $ in Thousands	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Union Center National Bank [Member]
Leverage (Tier 1) capital	$ 996,013	$ 891,730
Leverage (Tier 1) capital, ratio	0.1064	0.1143
Leverage (Tier 1) capital, capital adequacy	$ 374,553	$ 312,166
Leverage (Tier 1) capital, capital adequacy, ratio	0.0400	0.0400
Leverage (Tier 1) capital, well capitalized	$ 468,191	$ 390,207
Leverage (Tier 1) capital, well capitalized, ratio	0.0500	0.0500
CET one risk based capital	$ 996,013	$ 891,730
CET one risk based capital, ratio	0.1160	0.1196
CET one risk based capital, capital adequacy	$ 386,289	$ 335,641
CET one risk based capital, capital adequacy, ratio	0.0450	0.0450
CET one risk based capital, well capitalized	$ 557,972	$ 484,815
CET one risk based capital, well capitalized, ratio	0.0650	0.0650
Tier 1, risk based capital	$ 996,013	$ 891,730
Tier 1, risk based capital, ratio	0.1160	0.1196
Tier 1, risk based capital, capital adequacy	$ 515,051	$ 447,522
Tier 1, risk based capital, capital adequacy, ratio	0.0600	0.0600
Tier 1, risk based capital, well capitalized	$ 686,735	$ 596,696
Tier 1, risk based capital, well capitalized, ratio	0.0800	0.0800
Total capital	$ 1,117,733	$ 1,002,753
Total capital, ratio	0.1302	0.1344
Total capital, capital adequacy	$ 686,735	$ 596,696
Total capital, capital adequacy, ratio	0.0800	0.0800
Total capital, well capitalized	$ 858,419	$ 745,869
Total capital, well capitalized, ratio	0.1000	0.1000
Parent Company [Member]
Leverage (Tier 1) capital	$ 1,000,577	$ 909,577
Leverage (Tier 1) capital, ratio	0.1068	0.1165
Leverage (Tier 1) capital, capital adequacy	$ 374,729	$ 312,194
Leverage (Tier 1) capital, capital adequacy, ratio	0.0400	0.0400
CET one risk based capital	$ 884,495	$ 793,495
CET one risk based capital, ratio	0.1030	0.1064
CET one risk based capital, capital adequacy	$ 386,295	$ 335,648
CET one risk based capital, capital adequacy, ratio	0.0450	0.0450
Tier 1, risk based capital	$ 1,000,577	$ 909,577
Tier 1, risk based capital, ratio	0.1166	0.1219
Tier 1, risk based capital, capital adequacy	$ 515,061	$ 447,531
Tier 1, risk based capital, capital adequacy, ratio	0.0600	0.0600
Total capital	$ 1,240,047	$ 1,138,350
Total capital, ratio	0.1445	0.1526
Total capital, capital adequacy	$ 686,748	$ 596,708
Total capital, capital adequacy, ratio	0.0800	0.0800

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