Loans and Lease Finance Receivables and Allowance for Credit Losses - Summary of Recorded Investment in Collateral-Dependent loans (Detail) $ in Thousands	Mar. 31, 2021 USD ($) Collateral	Dec. 31, 2020 USD ($) Collateral
Financing Receivable, Modifications [Line Items]
Real Estate	$ 10,672	$ 10,712
Business Assets	8,385	6,653
Other	$ 311	$ 280
Number of Loans Dependent on Collateral | Collateral	46	41
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Real Estate	$ 7,689	$ 7,883
Business Assets	0	0
Other	$ 0	$ 0
Number of Loans Dependent on Collateral | Collateral	8	8
Construction [Member]
Financing Receivable, Modifications [Line Items]
Real Estate	$ 0	$ 0
Business Assets	0	0
Other	$ 0	$ 0
Number of Loans Dependent on Collateral | Collateral	11	0
Small Business Administration [Member]
Financing Receivable, Modifications [Line Items]
Real Estate	$ 1,826	$ 1,761
Business Assets	418	326
Other	$ 168	$ 185
Number of Loans Dependent on Collateral | Collateral	0	10
SBA - Paycheck Protection Program (PPP) [Member]
Financing Receivable, Modifications [Line Items]
Real Estate	$ 0	$ 0
Business Assets	0	0
Other	$ 0	$ 0
Number of Loans Dependent on Collateral | Collateral	0	0
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Real Estate	$ 421	$ 470
Business Assets	7,708	5,542
Other	$ 143	$ 95
Number of Loans Dependent on Collateral | Collateral	21	18
Dairy & Livestock and Agribusiness [Member]
Financing Receivable, Modifications [Line Items]
Real Estate	$ 0	$ 0
Business Assets	259	785
Other	$ 0	$ 0
Number of Loans Dependent on Collateral | Collateral	1	1
Municipal Lease Finance Receivables [Member]
Financing Receivable, Modifications [Line Items]
Real Estate	$ 0	$ 0
Business Assets	0	0
Other	$ 0	$ 0
Number of Loans Dependent on Collateral | Collateral	0	0
SFR Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Real Estate	$ 424	$ 430
Business Assets	0	0
Other	$ 0	$ 0
Number of Loans Dependent on Collateral | Collateral	2	2
Consumer and Other Loans [Member]
Financing Receivable, Modifications [Line Items]
Real Estate	$ 312	$ 168
Business Assets	0	0
Other	$ 0	$ 0
Number of Loans Dependent on Collateral | Collateral	3	2