Loans and Allowance for Credit Losses - Geographic and Collateral Concentration (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Geographical concentration | Loans, net
Concentration risk
Percentage of loan	100.00%	100.00%
Geographical concentration | Loans, net | Texas
Concentration risk
Percentage of loan	19.00%	18.60%
Geographical concentration | Loans, net | California
Concentration risk
Percentage of loan	11.80%	11.40%
Geographical concentration | Loans, net | Florida
Concentration risk
Percentage of loan	7.00%	6.40%
Geographical concentration | Loans, net | Georgia
Concentration risk
Percentage of loan	6.80%	7.10%
Geographical concentration | Loans, net | Arizona
Concentration risk
Percentage of loan	6.70%	6.10%
Geographical concentration | Loans, net | Oregon
Concentration risk
Percentage of loan	6.30%	5.90%
Geographical concentration | Loans, net | New York
Concentration risk
Percentage of loan	4.70%	4.80%
Geographical concentration | Loans, net | North Carolina
Concentration risk
Percentage of loan	4.40%	4.10%
Geographical concentration | Loans, net | Washington
Concentration risk
Percentage of loan	3.10%	3.40%
Geographical concentration | Loans, net | Ohio
Concentration risk
Percentage of loan	3.50%	3.20%
Geographical concentration | Loans, net | Other
Concentration risk
Percentage of loan	26.70%	29.00%
Collateral concentration
Concentration risk
Percentage of SBA loan	100.00%	100.00%
Collateral concentration | Lodging
Concentration risk
Percentage of SBA loan	23.10%	23.40%
Collateral concentration | Gasoline Service Stations
Concentration risk
Percentage of SBA loan	13.00%	12.80%
Collateral concentration | Eating Places
Concentration risk
Percentage of SBA loan	6.30%	6.20%
Collateral concentration | Child Day Care Services
Concentration risk
Percentage of SBA loan	5.60%	5.60%
Collateral concentration | Offices of Physicians
Concentration risk
Percentage of SBA loan	4.00%	4.10%
Collateral concentration | General Freight Trucking, Local
Concentration risk
Percentage of SBA loan	3.30%	3.50%
Collateral concentration | Grocery Stores
Concentration risk
Percentage of SBA loan	2.30%	2.30%
Collateral concentration | Coin-Operated Laundries and Drycleaners
Concentration risk
Percentage of SBA loan	1.90%	1.90%
Collateral concentration | Beer, Wine, and Liquor Stores
Concentration risk
Percentage of SBA loan	1.40%	1.30%
Collateral concentration | Funeral Service and Crematories
Concentration risk
Percentage of SBA loan	1.30%	1.40%
Collateral concentration | Other
Concentration risk
Percentage of SBA loan	37.80%	37.50%
Collateral concentration | Loans, net
Concentration risk
Percentage of loan	100.00%	100.00%
Collateral concentration | Loans, net | Multi-family
Concentration risk
Percentage of loan	62.40%	60.90%
Collateral concentration | Loans, net | SBA
Concentration risk
Percentage of loan	12.50%	11.40%
Collateral concentration | Loans, net | Mixed Use
Concentration risk
Percentage of loan	8.40%	8.40%
Collateral concentration | Loans, net | Industrial
Concentration risk
Percentage of loan	5.30%	4.30%
Collateral concentration | Loans, net | Office
Concentration risk
Percentage of loan	3.40%	4.40%
Collateral concentration | Loans, net | Retail
Concentration risk
Percentage of loan	4.00%	4.30%
Collateral concentration | Loans, net | Lodging
Concentration risk
Percentage of loan	1.40%	1.60%
Collateral concentration | Loans, net | Other
Concentration risk
Percentage of loan	2.60%	4.70%