Loans and Lease Finance Receivables and Allowance for Credit Losses - Summary of Loan, Including PCI Loans by Internal Risk Ratings (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 7,887,713	$ 8,348,808
Commercial And Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable gross	813,063	812,062
SBA [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable gross	288,600	303,896
Total loans	288,600	303,896
Commercial Real Estate Owner Occupied [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,131,800	2,143,259
SFR mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable gross	240,654	270,511
Total loans	240,654	270,511
Dairy & Livestock and Agribusiness [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable gross	386,219	361,146
Municipal Lease Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable gross	45,933	45,547
Total loans	45,933	45,547
Consumer and other loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable gross	74,665	86,006
Total loans	74,665	86,006
Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,639,436	8,046,192
Pass [Member] \| SBA [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	271,625	279,708
Pass [Member] \| SFR mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	238,189	266,441
Pass [Member] \| Municipal Lease Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	45,594	45,135
Pass [Member] \| Consumer and other loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	72,411	84,483
Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	192,175	223,797
Special Mention [Member] \| SBA [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	6,756	12,430
Special Mention [Member] \| SFR mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8	452
Special Mention [Member] \| Municipal Lease Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	339	412
Special Mention [Member] \| Consumer and other loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,983	630
Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	56,102	78,819
Substandard [Member] \| SBA [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	10,219	11,758
Substandard [Member] \| SFR mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,457	3,618
Substandard [Member] \| Municipal Lease Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0	0
Substandard [Member] \| Consumer and other loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	271	893
Doubtful & Loss [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0	0
Doubtful & Loss [Member] \| SBA [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0	0
Doubtful & Loss [Member] \| SFR mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0	0
Doubtful & Loss [Member] \| Municipal Lease Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0	0
Doubtful & Loss [Member] \| Consumer and other loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 0	$ 0